present:

Aeroflot Open, Moscow

Biel Master Tournament Open Special feature

Bosna, Sarajevo, former strong invitational, now a rather local Open Special feature

Canadian Open Chess Championship, at various venues

Cappelle-la-Grande Open, currently of rather local character

Chigorin Memorial, St. Petersburg, earlier a strong invitation series in Sochi

Czech Open, Pardubice

Dubai Open Sheikh Rashid Bin Hamdan Al Maktoum Cup Extras

Gibraltar Tradewise Masters, Catalan Bay / La Caleta current Superopen

Grenke Chess Open, Karlsruhe (following the Neckar-Open, Deizisau)

Hastings Chess Congress, former legendary invitation series, now Open Special feature

Isle of Man chess.com Masters, Port Erin, today in Douglas current Superopen

Politiken Cup, Xtracon Chess Open, Copenhagen, today in Helsingør

Reykjavik Open, starting as an invitation tournament series

Rilton Cup, Stockholm

Sharjah Masters

U.S. Open Chess Championship Special feature
(1st edition held in 1900, annually without any break!!)
in swiss system since the mid-1940s, at various venues

World Open, mainly in Philapelphia, early editions in New York,
later sometimes also in Arlington or other U.S. cities
 

past Superopen:

Lloyds Bank Masters, London, 1977-1994 An easy-to-read survey

18 consecutive editions: First winner in 1977 was Miguel Quinteros, last winner in 1994 young Alexander Morozevich, both outright

Lone Pine, California, 1971-1981 Louis D. Statham Tournament Full history

11 consecutive editions: First winner in 1971 was Larry Evans, last winner in 1981 Viktor Korchnoi, both outright; further winners, sole or shared, were Tigran Petrosian, Bent Larsen, Svetozar Gligoric (2x), Vladimir Liberzon (2x), Oscar Panno, Vlastimil Hort, Florin Gheorghiu, Dragutin Sahovic, Walter Browne, Arthur Bisguier, Roman Dzindzichashvili, and Nona Gaprindashvili

Lugano Open, Switzerland, 1976-1989 Exlusive in the web!

14 consecutive editions: First winner in 1976 was Gennadi Sosonko, last winner in 1989 Viktor Korchnoi (3x, plus one co-win); further winners included Yasser Seirawan (2x), Gyula Sax, Lubomir Ftacnik, Vladimir Tukmakov, Bojan Kurajica, Sergio Mariotti, as well as Nigel Short (co-winner), Kevin Spraggett (co-winner), or Eugenio Torre (co-winner). Many top ten / top twenty players participated: from Spassky to young Anand, Larsen, Miles, Nunn, Timman, Piket, Lautier, Hübner, Unzicker, Hort, Pachman, Gligoric, Ivkov, Szabo, Ribli, Adorjan, Gulko, De Firmian, Browne, Reshevsky and the strongest ladies, Lugano was really internationally mixed in gender and ages

New York Open, New York City, 1981-2000 (no editions '82, '99) Extended version to come

18 editions: First winner in 1981 was Lev Alburt, last winner in 2000 Ilya Smirin, both outright

Worth of mention:

OHRA Open, Amsterdam 1982-1990, 9 editions, strong Invitation Open series but with a field of (only) 24 to 32 players, then from 1985 to 1990, the Open was a side event of the OHRA Invitation tournament series at Amsterdam

recently cancelled or interrupted series:

Millionaire Chess (MC) Open, Las Vegas 2014 & 2015, Atlantic City 2016

Qatar Masters, Doha, 2014 & 2015

This is a listing of the about twenty strongest recurring international Open elite *series* in classical chess, from past and present.

Two longlasting series with an earlier peak time as a closed (invitation) elite tournament (the famous Hastings Chess Congresses, and Bosna in Sarajevo), both held as an Open today, are integrated, too. 

The rare Open series which attended regularly top ten ranked players, are named "Superopen" in analogy to the closed "Supertournament":

Summary:

Superopen series in classical chess, past & present
*listed in chronological order, at least five editions* 

Lone Pine, Louis D. Statham Tournament, California, 1971-1981

Lugano Open, Switzerland, 1976-1989 

Lloyds Bank Masters, London, 1977-1994

New York Open, New York City, 1981-2000 (no editions '82, '99)

Gibraltar Chess Congress Tradewise Masters (initially Gibtelecom Masters),
Catalan Bay / La Caleta, since 2003

Isle of Man Masters (IoM)
Monarch Assurance IoM, played in Port Erin, 1993-2007 (first series, moderate strong); 
PokerStars / Chess.com IoM, played in Douglas, relaunched in 2014 (Superopen)

A Chess Superopen series is big and diverse (strength and largeness of the top participating grandmasters and the status of the tournament in continuation), mixed in gender and ages, with players representing not only various countries, but also different continents.

By given definition, the overview is focussed on series and covers classical chess (no rapid / blitz of exhibition type). It's a best-effort, with a subjective component, no offense intended!

Seldom a one-off open tournament had been superstrong, too; i.e. the IBM Open in Vienna in January 1986, the first international Chess Open ever featuring two World Champions, and one of the very few Open in history with four current top ten players, or the somehow forgotten Alekhine Open Memorial in Moscow, held parallel to the Alekhine Invitation Memorial in 1992. Thus, these two stand alone Superopen from Vienna and Moscow are also presented briefly.

Apart from these tournaments open to everyone (grandmaster level), there were / are also official "open" tournaments, organised in swiss system, by name:

> Interzonal Manila 1990 

> Interzonal Biel 1993 

Both of these two last FIDE Interzonal tournaments (embedded in the World Chess Championship cycle), within a relatively large field of more than 60 strong players

> GMA Open (qualification) 1988-89; 1990
Belgrade, Moscow, Palma de Mallorca; Moscow

> PCA Open (qualifying) 1993 Groningen

> FIDE Grand Prix (qualification cycle) 2017, 
Sharjah, Moscow, Geneva, Palma de Mallorca
four GP, within a small field of 18 players each!

The format changed from a round robin (all-play-all) to a swiss system for the 2017 World Chess FIDE GP. In contrast to the previous editions where players played a full round-robin, each GP is now a 18-player, 9-round Swiss and players will each appear in three of the four GP tournaments (organised by AGON for FIDE).

The World Chess FIDE Grand Prix 2017 is a series of four chess tournaments with in total 24 players participating in the whole cycle, that form part of the qualification cycle for the World Chess Championship: The top two finishers (point scoring overall) will qualify for the 2018 Candidates Tournament.

> Team competitions, especially the biannually played Chess Olympiad since 1976 in Haifa, or the European Team Chess Championship (ETCC) since 1989 in Haifa, European Chess Club Cup, etc.

> World Junior Chess Championships (mostly) and World Senior Chess Championships

> National Championships in some countries (for instance, Switzerland has an alternate rhythm)

Swiss system: Pairing system invented by Dr. J. Müller of Brugg, Switzerland, and first used in a chess tournament at Zurich in 1895.

George Koltanowski later introduced the Swiss System in the United States.

The first use of the Swiss system in the United States was the Texas Championship in 1942.

The first national event to use the Swiss system was the 1945 U.S. Intercollegiate Championship.

Since 1947 every (annually played) U.S. Open has been conducted under the Swiss System.

The first Swiss System at the Chess Olympiad (biannual team event) was Haifa, Israel in 1976.

George Koltanowski: The man who established the Swiss System in chess competitions

George Koltanowski, a Belgian-born American chess player, promoter, organizer, arbiter, and writer, was awarded the International Master title in 1950 when the title was first officially established by FIDE, and he was awarded an Honorary Grandmaster title in 1988.

He showed up for the 1946 U.S. Open Chess Championship (U.S. Open) in Pittsburgh, but was eliminated in the preliminary section and did not qualify for the finals.

The 47th U.S. Open in 1946, played in Pittsburgh was for the first time using the swiss system to determine different final sections in round robin.

In those years, the U.S. Open was played in round-robin preliminary and final sections. However, the next year, George Koltanowski returned, not as a player but as the director, introducing the Swiss system to the U.S. Open. He directed the 1947 U.S. Open in Corpus Christi, Texas, using the Swiss system for the first time ever in a U.S. Open chess event as a whole.

After that, Koltanowski traversed the country, holding Swiss system tournaments everywhere. Before long, the Swiss system was adopted as the standard for most chess tournaments in America, and Open Festivals worldwide. 

Definition & Explanation: https://www.thespruce.com/the-swiss-system-611537 (Edward Scimia), https://www.chess.com/chessopedia/view/swiss-system (Bill Wall), Swiss system (Wikipedia), https://www.fide.com/fide/handbook.html?id=83&view=article (FIDE Handbook, pairing rules)

1.-2. Korchnoi at age of 55 (winner on tie-break scores), and Beliavsky; ahead of Ftacnik (3.-9., third on tie-break), Karpov, Gheorghiu, Nunn, Quinteros, Garcia-Palermo, Spassky; Chandler, Dückstein, Züger, Danner, Kindermann, Klinger, Farago, Schüssler, Matanovic, Mednis, Borik; Zsuzsa Polgar, Helene Mira, among others

Four reigning top ten players of the world in an Open competing: Karpov (#2), Korchnoi (#6), Beliavsky (#7=), and Spassky (#9=), followed by Nunn (#top twenty of Elo list January 1986).

Karpov (white) and Korchnoi (black) drew their individual encounter at IBM-Vienna Open, a hard-fought game: http://www.chessgames.com/perl/chessgame?gid=1068520.

IBM-Invitation Open tournament in January 1986, based on the model of Lone Pine, nine rounds swiss system, 48 invited participants in an international mix of absolute superstars, youngsters, female players and some local heroes (Austria, Germany, Switzerland).

One of the very few times, Anatoly Karpov playing an Open in classical chess (he remained unbeaten but with six draws out of nine games and was upset to be paired with too many 'minor' players due to swiss system). DIE SCHACHWOCHE no. 3 & no. 4 / 1986, and GM Robert Byrne,
http://www.nytimes.com/1986/04/08/nyregion/chess-vienna-ibm-contest-won-by-korchnoi-and-belyavsky.html

In 1992 (100th anniversary of Alexander Alekhine, Alekhine Festival), there was held an additional Alekhine Memorial Open in Moscow, won by Sergei Tiviakov (then Russia) as clear first, ahead of Epishin, in a strong field with – among others – Aseev, Ehlvest, Malaniuk, Serper, Yudasin, Kramnik, Dolmatov, Oll, Sveshnikov, Sakeev, Smirin, Psakhis, Dreev, Sveshnikov, M. Gurevich, Kuzmin, Smyslov, Tseshkovsky, Xie Jun, Svidler, Akopian, Bagirov, Savon, Gipslis, Geller, Kholmov.

Watch out: http://al20102007.narod.ru/it/1992/al_ope92.html (60 players)

Of course, it was nearly national, but a very strong and compact line-up. A big achievement for young Tiviakov!

The Open was running parallel to the closed invitation tournament (with Botvinnik, Najdorf, and Lilienthal forming the jury!), won jointly by 1.-2. Anand and Gelfand, followed by 3. Kamsky, 4.-6. Karpov, Salov, Jussupow, 7. Shirov, and 8. Timman.

Tiviakov, the Traveller: Sergei somehow manages to (i) travel to the most exotic places in the world, (ii) win or co-win the tournaments staged there, and (iii) send the chess community a huge batch of photos he has taken during his stay. His illustrated reports and pictorial impressions, are always a highlight. Although he has considered himself a professional chess player since 1989, Tiviakov also finished his degree in agricultural economics.

Before studying the game, please have a look at his lively chess career. Tiviakov is certainly one of the strongest sub-2700 ELO players just one step beyond the very best, quite regular top hundred player since the early 1990s, his peak ranking is no. 14/15 of the world in July - December 1995; a decade later, in October - December 2005, ranked as no. 20, he has been one ELO point away from reaching the (today) notorious 2700 milestone.

Sergei Tiviakov, born in Krasnador in 1973, settled to Groningen in 1997.
Member of the Smyslov school. IM since 1990. GM since 1991.

For a selection of his tournament wins: http://www.chessdiagonals.ch/402840528 (scroll down)

Biel Chess Festival regularly offers both, a closed invitation tournament (round robin) and an open tournament (swiss system) of high level calibre; the large and strong Open (MTO), sometimes forgotten / outshined by the Invitational (GMT), including three Interzonals.

Thus the near complete (really complete!) elite of the last forty years played at Biel Chess Festival in one or the other way – a feat only matched by Wijk aan Zee with its A,B,C groups.

As mentioned, the former world-class tournaments of Hastings and Sarajevo (Bosna) are now played in a swiss system and lost their previous stardom.

Glory and fame of a tournament (series) seem sometimes unpredictable, there are so many imponderabilities in economic life, well, in life in general 🙃 

This has not necessarily to do with a format change, other factors count as well: an excellent combination of serious chess, playing conditions, organisation, sightseeing, location, good food, sponsoring, prize money, time, duration, media coverage and reception, the love and respect for the players!!

Reykjavik for instance gained much on reputation in status and strength after switching from a closed invitational tournament to an Open Festival today. As Gibraltar Tradewise, Isle of Man, Moscow Aeroflot, Dubai or Doha (Qatar Masters) it is proof, that an Open can successfully be launched on a high level, big and diverse. They have reached the status of a supertournament, too, and are offering several hundred of rated players to join the chess community.

Those were the days, Lone Pine, California in the '70ies (1971 until 1981), Llyods Bank Masters Open in London (1977 - 1994), New York Open (1981 - 2000) and maybe foremost the Lugano Open Festival series (1976 - 1989), especially in the '80ies, can be regarded as the prominent predecessors and perfect role model of the Gibraltar Tradewise Masters Chess Congress, the relaunched Isle of Man Open, Aeroflot Open in Moscow, Dubai or Reykjavik Open today.
 

Chessdiagonals reveals exclusively the Top Twenty-Five Open series in classical chess of past and present, ordered alphabetically.

http://www.acfed.ru/tournament/aeroflot-open-2017/ (Official Site)

https://en.wikipedia.org/wiki/Aeroflot_Open (Wikipedia)

The Aeroflot Open is an annual open chess tournament played in Moscow and sponsored by the airline Aeroflot. It was established in 2002 and quickly grew to be one of the strongest open chess tournament; 2013 it was converted to a rapid and blitz event, while in 2014 it wasn't held.

The winner is invited to the Dortmund chess tournament held later in the same year, a tradition begun in 2003. Beside the main tournament (A Group), there are also B and C-class tournaments at Aeroflot Open.

Record winner is Ian Nepomniachtchi. He won 2008 and 2015 the Aeroflot Open in classical chess plus the 2013 edition blitz event.

http://www.bielchessfestival.ch/en/home/ (Official Site in english)

http://www.bielchessfestival.ch/fr/home/ (Official Site in french)

http://www.bielchessfestival.ch/de/home/ (Official Site in german)

https://en.wikipedia.org/wiki/Biel_Chess_Festival (Wikipedia)

Biel Festival - www.chessdiagonals.ch (overview)

Winners at Biel - www.chessdiagonals.ch (scroll down)

http://skbosna.ba/index.php/en/ (Official Site)

Sarajevo *1957 - www.chessdiagonals.ch

(No Wikipedia english entry so far)

https://en.wikipedia.org/wiki/Canadian_Open_Chess_Championship (Wikipedia)

Played at various venues in  Canada. Not to mix with the national Canadian Chess Championship.

The Canadian Open Chess Championship is Canada's international Open chess championship, launched in 1956, and held annually since 1973, usually in mid-summer. It is organized by the Chess Federation of Canada. The event celebrated its 50th rendition in 2013.

It was organized every two years from 1956 until 1970, and afterwards annually. In 2015, no tournament was held. Since 2016, the Open takes part again, but ultimately, it became a more national event.

The tournament rotates around the country, and has been held in seven of Canada's ten provinces during its 60-year history. The format has usually been a Swiss system with nine or ten rounds, usually over a nine-day period. It is open to all players who wish to enter, from Grandmasters to beginners.

The Championship's list of winners has included some of the world's strongest players, including Grandmasters Boris Spassky (in 1971, while he was World chess champion), Bent Larsen, Alexei Shirov, Vassily Ivanchuk, Viktor Bologan, Artur Yusupov, Bu Xiangzhi, Alexander Moiseenko, Kevin Spraggett, Ljubomir Ljubojević, Larry Evans, Pal Benko, William Lombardy, Gyula Sax, Igor Ivanov, Walter Browne, Tony Miles, Larry Christiansen, Joel Benjamin, Eduardas Rozentalis, Vladimir Tukmakov, Jonathan Rowson, Luke McShane, Vladimir Epishin, Vladimir Malaniuk, Pentala Harikrishna, Alexander Shabalov, Nigel Short, Eric Hansen, and many other top stars.

Toronto has hosted the most Canadian Opens with ten, followed by Ottawa with seven and Edmonton with six (as of 2014).

Montreal 1974 saw the largest attendance to date, with 648 players. Ottawa 2007 set a tournament record with 22 Grandmasters participating.

The first tournament in Montreal 1956 was noteworthy for the presence of 13-year-young prodigy Bobby Fischer, a future World chess champion, who tied for 8-12th places.

Laszlo Witt made the only perfect score (9-0) at Ottawa 1962.

Mark Bluvshtein is the youngest champion, at age 17 at Edmonton in 2005. Daniel Yanofsky was the oldest champion, at age 54, also in Edmonton in 1979.

Canadian Grandmaster Kevin Spraggett has the record for most titles with eight (either clear first or shared).

http://www.cappelle-chess.fr/en2/default.php (Official Site)

https://en.wikipedia.org/wiki/Cappelle-la-Grande_Open (Wikiepdia in english)

https://fr.wikipedia.org/wiki/Open_de_Cappelle-la-Grande (Wikipedia in french)

The Cappelle-la-Grande Open is a chess tournament held every year in Cappelle-la-Grande, France, since 1985.

The tournament is usually played in the second half of February with an accelerated Swiss-system format in nine rounds. It is organized by the chess club L'Echiquier Cappellois and is played in the Palais des Arts of Cappelle-la-Grande.

It has become over the years one of the largest opens in the world, but in terms of average player strength slightly behind the Giants.

For instance, the edition in 2010 of the colossal Cappelle-la-Grande series had 652 participants, with 82 Grandmasters and 61 International Masters from 57 countries.

Unfortunatley, the tournament faced a near-collapse in 2017, and is reduced to a smaller event due to financial problems.

Record five-time winner is Mark Hebden (in 1989, 1990, 1994, 1995 and 1997, always shared).

The Chigorin Memorial Tournament in St. Petersburg, Russia, has had a long tradition. It is named after the first influencer of the Soviet Chess School, Mikhail Chigorin, one of the leading players of his time and the major source of inspiration for the "Soviet School of Chess", which dominated the chess world in the middle and latter parts of the 20th century.

Akiba Rubinstein, Emanuel Lasker, Mikhail Botvinnik, Vassily Smyslov, Mikhail Tal, Boris Spassky, Svetozar Gligoric, Mark Taimanov, Lev Polugaevsky, and Viktor Korchnoi — each of them did something special that changed our sport in numerous ways. They may have all passed away, but their ideas still lead generations of chessplayers forward. Something else is common between these greats: All have won the Chigorin Memorial tournament at some point in their lives, and many more prominent players from Alexander Beliavsky (closed series) to Alexander Grischuk (open series).

Note: The initial closed editions in St. Petersburg 1909, and the following Sochi series of invitation tournaments are not to mix with the later and ongoing Open tournament series in St. Petersburg!

Overall survey: https://en.wikipedia.org/wiki/Chigorin_Memorial

First Chigorin Memorial in St. Petersburg (Invitation tournament)

The very first and most important edition was organised in 1909 in Saint Petersburg, a year after Chigorin had died.

Rubinstein and Lasker won 875 rubles (each) prize money as joint winners of this world elite chess tournament, Spielmann and Duras earned 475 rubles (each) on third / fourth place, Bernstein as fifth got 190 rubles, Teichmann, for once, finished sixth in a super strong field (incl. Schlechter, Tartakower, Mieses, Burn, Vidmar, or Eugene Znosko-Borovsky who finished 19th and last).

Further unregular Memorial invitation tournaments had been held in 1947, 1951, 1961, and 1972, played in diverse venues.

Sochi series (Closed series)

Later on, an international invitation Memorial series was established, and mainly played in the Black Sea resort Sochi (1963 to 1990).

Record winner of the strong international invitation Chigorin Memorial is Lev Polugaevsky who won four times, in 1963, 1974, and 1976 always in Sochi, plus 1972 in Kislovodsk.

Viktor Korchnoi won in 1966 (Polugaevsky sole second, Spassky shared fifth-sixth with Lein).

St. Petersburg (Open series)

From 1993 the venue returned to his hometown, since 1993, the Chigorin Memorial has been organised as an Open (swiss system). Note: A 13th edition was not played for superstitious reasons.

Record winners of the ongoing Open series are Sergey Volkov who (co-)won in 1998, 1999, 2009, and Kirill Alekseenko who is now a triple winner of the Chigorin Memorial. He claimed clear first or first on tie-break in 2015, 2016 & 2017:

https://en.chessbase.com/post/kirill-alekseenko-wins-chigorin-memorial 
(ChessBase, Chigorin Memorial 2015)

https://en.chessbase.com/post/chigorin-memorial-alekseenko-wins-abdusattorov-shines (ChessBase, Chigorin Memorial 2016)

https://en.chessbase.com/post/suspense-will-nodirbek-make-it
(ChessBase, Chigorin Memorial 2017)

The yearly Chigorin Memorial Open had been played later from 21st to 29th October 2017 at St. Petersburg, too. Kirill Alekseenko edged out David Paravyan, SP Sethuraman and Alexey Sarana on tie-break after all scored 7.5/9. Many participants of the massive horde of strong 'anonymous' players from the former Soviet areas, and promising youngsters:

By securing his third and final gm norm, 13 year young Nodirbek Abdusattorov of Uzbekistan became the second youngest grandmaster in chess history (as of 2017). Only Sergey Karjakin got the title at a younger age. Nordirbek Abdusattorov was the then youngest living grandmaster in the world.

Nordirbek Abdusattorov , born 18 September 2004, fulfilled all requirements for the grandmaster title on 29 October 2017, at the age of 13 years, 1 month and 11 days. That was faster than Parimarjan Negi  from India, who became a grandmaster at 13 years, 4 months and 22 days, and Magnus Carlsen  from Norway, who got the title at 13 years, 4 months and 27 days.

The record, as mentioned above, is still in the hands of Sergey Karjakin  (then Ukraine, today Russia), who became a gm when he was 12 years, 7 months and 0 days.

http://www.dubaichess.ae/ (Official Site)

https://en.wikipedia.org/wiki/Dubai_Open_Chess_Tournament (Wikipedia)

The Dubai Chess Festival started in 1999 and is one of the world's premier open events:

Magnus Carlsen earned his final GM norm at Dubai in 2004, Wang Hao claimed the Dubai Open in 2005 as an untitled player above more than 50 GMs, Wesley So won his first major event at Dubai in 2008. Gawain Jones from England is the first player to defend his champion title successfully, as double winner in 2016 and 2017.

Dubai Chess and Culture Club, UAE

The Dubai Chess and Culture Club, United Arab Emirates was established in 1979 as a part of the UAE Chess Federation, the governing body of chess in the UAE, and was officially recognized as an independent entity on May 16, 1981. The club’s headquarters was originally located in Burj Nahar in Deira District before it was moved permanently to its current location in Al Mamzar, Dubai.

The club's current headquarters was built on May 2, 1999 and was widely acknowledged as the most modern and biggest dedicated chess club in the world when it was completed. The building is designed in the shape of a rook.

Sheikh Hamdan Bin Rashid Al Maktourm, Deputy Ruler of Dubai and Minister of Finance, is the honorary president of the Club. Sheikh Hamdan has played a major role in supporting the chess movement in the region. Some of the most notable members of the club include Saeed Ahmed Saeed, the UAE’s first world champion in chess and first IM, and Taleb Moussa, the UAE’s first GM.

The club played a major role in organizing the 27th World Chess Olympiad in 1986, which was hosted by the UAE Chess Federation at the Dubai World Trade Centre, and has organized other international chess events such as the 2014 World Rapid and Blitz Championships, Asian Cities Championships, Arab Championships and since 1999 the annual Dubai Open.

http://www.gibraltarchesscongress.com/ (Official Site)

https://en.wikipedia.org/wiki/Gibraltar_Chess_Festival (Wikipedia)

History & Highlights

Great Britain series - www.chessdiagonals.ch

http://www.hastingschess.com/ (Official Site)

https://en.wikipedia.org/wiki/Hastings_International_Chess_Congress (Wikipedia)

Pictorial Overview

Hastings *1920/21 - www.chessdiagonals.ch

Great Britain series - www.chessdiagonals.ch

http://iominternationalchess.com/ (Official Site)

https://www.facebook.com/iominternationalchess/ (IoM Official Facebook)

https://twitter.com/iomchess?lang=de (IoM Official Twitter)

https://www.visitisleofman.com/ (Official Visitor Website)

http://www.visitiom.co.uk/events/isle-of-man-international-chess-tournament/

Isle of Man Open has been played under three different labels:

Monarch Assurance IoM in Port Erin (1993 - 2007)
PokerStars IoM in Douglas (2014 - 2015)
Chess.com IoM in Douglas (since 2016)

Top tens Caruana, Nakamura & So played at IoM in 2016, Eljanov won on tie-break above Caruana.

In 2017, World Chess Champion Magnus Carlsen (world no.1); ex-World Champion Vladimir Kramnik (world no.3); Fabiano Caruana (world no.5); ex-World Champion Viswanathan Anand (world no.7); Hikaru Nakamura (world no.10 in the official FIDE Elo rating list of september 2017), covering for the first time five top ten players in an open tournament (non-official swiss system)!

Carlsen won outright (en passant, in individual games, he beat both winners from the previous year, Eljanov and Caruana); plus presented proudly his girlfriend, 22-year-old Synne Christin Larsen. Magnus and Synne have been in a relationship since the Valentine's Day of 2017. At IoM, it was the first time that Magnus Carlsen and his girlfriend were present in public. Prior to that around March he had changed his Facebook personal profile relationship status.

Reminiscences (Isle of Man Open has no Wikipedia entry so far):

Great Britain series - www.chessdiagonals.ch

http://www.grenkechessopen.de/en/ (Official Site in english)

http://www.grenkechessopen.de/de/ (Official Site in german)

Grenke Open, Karlsruhe, is following since 2016 (1st edition) the longtime running
Neckar-Open, Deizisau, 1997 – 2015 (19 editions)

http://neckar-open.de/index.php/ (former Official Site, still active)

https://de.wikipedia.org/wiki/Neckar-Open (Wikipedia)

In 2002, ten players (!) finished with 7/9, Vladimir Epishin won the A-Open by tiebreak:
http://theweekinchess.com/html/twic389.html#19

In 2007, Marie Sebag, was co-winner in a four-way tie, with Bu Xiangzhi as first:
http://www.neckar-open.de/images/swisschess/11noa-Rang-R9.htm

Prominent players at Deizisau: Benjamin (1999: 3), Christiansen (2000: 15.), Vaganian (2000: 6.), Aronian (2002: 5.), Sax (2002: 17.), Kasimdzhanov (2004: 1.), Eljanov (2004: 3.) Giri (2009: 60.), Naiditsch (2009–2015; best result 2011: 1.), Bacrot (2011–2015; best result 2013: 2.), Rapport (2008, 2012–2014; best result 2013: 1.) or Li Chao (2015: 1). Falko Bindrich took clear first 2008.

Note:

Grenke Open is not to mix with the closed Grenke Chess Classic, held unregularly at Baden-Baden / Karlsruhe, sometimes as national, sometimes as international invitation tournament

http://www.grenkechessclassic.com/de/ (Official Site)

https://en.wikipedia.org/wiki/Grenke_Chess_Classic (Wikipedia)

The Lloyds Bank Masters was a strong Open (swiss system) tournament series sponsored by Lloyds Bank, United Kingdom, organised during each summer in London from 1977 to 1994.

The winners (including the co-winners): 1977 (inaugural edition of the series) Miguel Quinteros (clear first at 8/10, Birnboim second, above joint third to fifth Torre, Nunn, and Webb; 68 players), 1978 John Peters, USA (making a GM norm), Rantanen, Littlewood (three-way tie), 1979 Murray Chandler, Westerinen, Haik (three-way tie), 1980 Florin Gheorghiu, Chandler, Ligterink (three-way tie), 1981 Raymond Keene, Seirawan, Miles (three-way tie), 1982 Anthony Miles, Gutman, Hort, Hebden, Johansen from Australia (five-way tie), 1983 Yuri Razuvaev, Nunn, Matanovic, William Watson (four-way tie), 1984 John Nunn, Chandler, Kudrin, Miles, Spassky (five-way tie), 1985 Alexander Beliavsky (then no. 3= of the world), 1986 Simen Agdestein, 1987 Michael Wilder (after play-off over Chandler), 1988, Garry Lane (after play-off over Adams), 1989 Zurab Azmaiparashvili, 1990 Stuart Conquest, Adams, Sturua (three-way tie), 1991 Alexey Shirov (just after winning the Biel GMT), 1992 Jonathan Speelman (first on tie-break above grandmaster Gennadi Timoshchenko), 1993 Jonathan Speelman (clear first ahead of 2./3. Miles, Nunn), 1994 (last edition) young Alexander Morozevich (clear first at amazing 9.5/10!). 

Note: Sometimes shared winners, in case of a tie, mostly the Buchholz tie-break score was used, but in some years, a play-off between the two leading players had been organised. 

In the first two editions '77 & '78, and again from 1987 on, ten rounds had been played at Lloyds Bank Masters in London, from 1979 to 1986, the Open was organized with nine rounds (swiss system).

Prize money wasn't that impressive, i.e. 1'200 £ for the clear winner in the year 1985.

Reminiscences (Lloyds Bank Masters has no Wikipedia entry so far):

Great Britain series - www.chessdiagonals.ch

Lone Pine International was a series of chess tournaments held annually in March or April from 1971 through 1981 in Lone Pine, California. Sponsored by Louis D. Statham (1907–1983), millionaire engineer and inventor of medical instruments, the tournaments were formally titled the Louis D. Statham Masters. The events were seven- to ten-round Swiss system tournaments, with entrance requirements that made them the strongest recurring Swiss tournaments in the U.S. in the 1980s. Former United States Champion and Grandmaster Isaac Kashdan served as the tournament director.

https://en.wikipedia.org/wiki/Lone_Pine_International (Wikipedia)

Year-by-Year statistics (Chessgames)

First winner in 1971 was Larry Evans, last winner in 1981 Viktor Korchnoi, among the winners, sole or shared, Tigran Petrosian, Bent Larsen, Svetozar Gligoric (2x), Vladimir Liberzon (2x), Oscar Panno, Vlastimil Hort, Florin Gheorghiu, Walter Browne, Arthur Bisguier, and Nona Gaprindashvili

http://www.chessgames.com/perl/chess.pl?tid=80794 (1971)
http://www.chessgames.com/perl/chess.pl?tid=80748 (1972)
http://www.chessgames.com/perl/chess.pl?tid=80952 (1973)
http://www.chessgames.com/perl/chess.pl?tid=80953 (1974)
http://www.chessgames.com/perl/chess.pl?tid=80676 (1975)
http://www.chessgames.com/perl/chess.pl?tid=80955 (1976)
http://www.chessgames.com/perl/chess.pl?tid=80958 (1977)
http://www.chessgames.com/perl/chess.pl?tid=81012 (1978)
http://www.chessgames.com/perl/chess.pl?tid=80680 (1979)
http://www.chessgames.com/perl/chess.pl?tid=81014 (1980)
http://www.chessgames.com/perl/chess.pl?tid=81016 (1981)
http://www.chessgames.com/perl/chesscollection?cid=1012379 (game compilation)

Lone Pine: Viktor Korchnoi and the Soviets

When GM Korchnoi was invited at Lone Pine in 1979, Oleg Romanishin and Vitaly Tseshkovsky were slated to play, but then it was discovered that Viktor Korchnoi would also be playing, and the Soviet authorities cancelled their entries.  

In 1981, Korchnoi entered the Lone Pine Open inkognito,  and won a spectacular game against Jussupow and the tournament as clear first. Besides this exception, Korchnoi has only faced Soviet players in official FIDE competitions after Amsterdam IBM in 1976 (won with Miles) until the end of boycott, Herceg Novi, Blitz in 1983 (Korchnoi clear runner-up after Kasparov), and Wijk aan Zee in 1984 (won with Beliavksy).

As a result of these boycotts, Korchnoi lacked the possibility to play most of the strongest opponents apart from the Candidate's cycle, ie. no game in classical chess with Tal between the year 1975 and Titograd 1984. No competitive game with young and promising Kasparov before they met at the official Chess Olympiad in 1982.

That means, no invitation for Viktor Korchnoi to estimated 40 possible international chess tournaments from 1976 up to 1983 because of boycott against him by the former Soviet Union.

Lone Pine: Alla Kushnir

Alla Kushnir was the first woman ever to compete at Lone Pine  – and she defeated GM Larry Evans in the first round of the event. Later she defeated also GM Istvan Bilek and Jeremy Silman, too.

Kushnir was the only woman IM at Lone Pine Tournament 1975. She came over from Israel with her other Ex-Russian compatriots, Vladimir Liberzon and Leonid Shamkovich. She had been the previous challenger three times in a row against Nona Gaprindashvili. Kushnir was the second ranking woman chess player in the world but in order to expedite her move to Israel in 1974 from the Soviet Union, she had to agree not to enter the current cycle for Woman’s World Championship.

Among the GM's, she drew against Reshevsky, Csom and Robatsch and beat GM Bilek of Hungary and most notably, the upset in round one against American GM Larry Evans. This must have been the fire lit to drive him to place second in this event. She finished the Lone Pine Open 1975 with 5 points following in total 3 wins, 4 draws and 3 losses.

In the Soviet Union, men and women were strictly separated and not allowed to play each other (decadence!). Kushnir's otb meeting with Evans was the first top-level tournament chess game where a woman played a man since the days of Vera Menchik. 

Vera Menchik (16 February 1906 – 27 June 1944) was a British-Czech chess player who gained renown as the world's first women's chess champion. She also competed in chess tournaments with some of the world's leading male chess masters, defeating many of them, including future World Champion Max Euwe.  

In 1944, during one of the last German air attacks on London, the 38-year-old Vera, who was widowed the previous year, still holding the title of women's world champion, her sister Olga, and their mother were killed in a V-1 flying bomb attack which destroyed their home in the Clapham area of South London.  

Subsequently, in 1976, FIDE decided to award Women Grandmaster titles, too. Kushnir earned her WGM title, among a few other female players that inauguration year.

In 1977, Georgian Nona Gaprindashvili (USSR) took part at Lone Pine, and co-won, alongside with Balashov, Panno, and surprising Sahovic.

R.I.P., Alla Kushnir (1941 - 2013).

A legendary Open chess tournament, and one of the strongest Open series ever held, sponsored by the Banca del Gottardo, from 1976 to 1989 annually played in March in the beautiful (Swiss-Italian Tyrolian) Prealps town of Lugano, Ticino. Principal initiator and organiser was Alois Nagler from the SG Zürich.

Lugano had a great Narrative: mixed gender and ages (legends and youth, both together), different styles and countries, plus prominent and promising players from the hosting nation.

Open Scacchistico Internazionale di Lugano 1976 – 1989
(Palazzo dei Congressi di Lugano, Patrocinato dalla Banca del Gottardo) 

• Players: Spassky, Korchnoi, Larsen, Hübner, Unzicker, Teschner, Timman, Sosonko, Piket, Miles, Short, Nunn, Hort, Pachman, Ftáčnik, Sax, Ribli, Adorjan, Szabo, Flesch, Gligoric, Ivkov, Nikolic, Kurajica, Georgiev, Gheorghiu, Soos, Balashov, Tukmakov, Psakhis, Gulko, Mednis, Reshevsky, Browne, Seirawan, De Firmian, Spraggett, Quinteros, Nogueiras, Chandler, Torre, Westerinen, Petursson, Dückstein, Tóth, Mariotti, Lautier, and Anand as reigning Junior World Chess Champion, amongst many others plus Karpov for a closed side blitz event in 1988, and
• Maia Chiburdanidze, Tatjana Lematschko, Alisa Marić, Suzana Maksimovic, Julia Arias, Jana Miles, Pia & her older brother IM Dan Cramling (Swedish champion in 1981), played in the Lugano Open, a role model for forthcoming events.

First winner at in 1976 was Gennadi Sosonko, last winner in 1989 Viktor Korchnoi (winning 1982, 1986, 1989, and 3rd (shared 1.-7.) in 1988, within five entries), among the winners Yasser Seirawan (2x winner within six entries), Gyula Sax, Lubomir Ftacnik, Vladimir Tukmakov, Bojan Kurajica, Sergio Mariotti, as well as Nigel Short (co-winner), Kevin Spraggett (co-winner), or Eugenio Torre (co-winner).

Lugano Open 1989, Auszug aus der Rangliste:

1. Kortschnoi mit 8/9 P. im 1. Rang; mit Petursson punktgleich im zweiten Rang; ganze 1.5 Punkte (!) vor 3.(=) IM Lautier (der amtierende Junioren-Weltmeister von 1988), 4. De Firmian, 5. Gheorghiu, 6. Miles, ... 30. Sax, 31. Nunn, ... 34. Ftáčnik, ... 36. Nikolic, ... 40. Torre, ... 43. GM Maja Tschiburdanidse (amtierende Weltmeisterin 5.5/9P.), ... 46. Seirawan, ... 57. Hübner (mit 5/9P.), ... 81. Tukmakow, ... 86. Larsen (mit 4.5/9P.), ua. 184 TeilnehmerInnen Meisterturnier, 208 TeilnehmerInnen Hauptturnier.

Lugano Open series (1976-89), big and diverse, a leading Open series in the 1980s: 

History: Lugano Open - www.chessdiagonals.ch Exlusive in the web!

http://www.millionairechess.com/ (Official Website)

https://en.wikipedia.org/wiki/Millionaire_Chess (Wikipedia)

Winners: Wesley So (2014), Hikaru Nakamura (2015), and Dariusz Świercz from Poland (2016).

 

• The first New York Open was held on the July 4th weekend, 1981- at the Casa de Espana in New York City
• The prize fund was $36,000, and the tournament was won by GM Lev Alburt of the United States, with 300 players participating (all sections together)
• In 1983, the New York Open came back with an unprecedented prize fund of $100,000, and created a revolution in tournament chess
• Up to that time, the largest tournament prize fund ever offered in the United States was $50,000. Thus, the New York Open could be considered the "father" of all big money open chess tournaments in the U.S., and even world wide
• Three former World Champions (Spassky, Smyslov, Tal) playing
• All three Polgar sisters played same year in the New York Open!!!
• The New York Open has always been run with the emphasis on quality. The goal has always been to make the best tournament possible, not to just try and make money
• More than two Hundred Grandmasters have participated in total
• Almost $2,000,000 paid out to players in prizes
• Players have come from at least 48 different countries
• This includes Cuba, the first time any of their chess players have played in the USA since Castro came to power in Cuba
• Every April, the “Big Apple” NYO was the greatest chess show on earth. Major national and international multimedia coverage: Television and front page newspapers across the world
• Organizer: José Cuchi from Spain, President of “Heraldica Imports”

(No Wikipedia entry so far)

Record winner: Lev Alburt with three wins or co-wins.

Winners, sole or shared (full list):

1981 (first edition) Alburt, 1982 no edition, 1983 Alburt, Miles, Browne, IM Shirazi, IM Kudrin (five players), 1984 Dzindzichashvili, 1985 Ljubojevic, Seirawan, Christiansen, Kudrin, IM De Firmian, IM Dlugy (six players) 1986 Smejkal, Sax 1987 Seirawan, Adorjan, 1988 Ivanchuk, 1989 Fedorowicz, 1990 IM Khalifman, 1991 Goldin, 1992 Lobron, 1993 Goldin, Ehlvest, Benjamin, Alburt, Adianto, Hellers, IM Ilya Gurevich (seven players), 1994 Ehlvest, Oll, 1995 Blatny, 1996 Van Wely, 1997 Bologan, Krasenkow, 1998 Minasian, 1999 no edition, 2000 (last edition) Smirin

(Korchnoi, Karpov, Kasparov, Anand, Kramnik never played)

The OHRA Chess Festival was organized and sponsored by the OHRA an insurance company, in Amsterdam, The Netherlands, and held from 1982 to 1990. The first three years, there was a strong but small Open within a field of 24 to 32 (invited) players, a mix between top players and local Dutch participants. From 1985 on, there had been an international invitation supertournament as well, the closed Crown group, overshadowing the Open somehow.

Hort (on tie-break), and Short won the inaugural Open event in 1982, Chandler (on tie-break), and Sax won in 1983, Timman won above runner-up Portisch in 1984. 

From 1985 on, the Open was now labelled as B-group. The winners were Hellers (1985), Zapata (1986), Hort (1987), Gulko, Gelfand, and Lobron (1988), Azmaiparashvili, and Psakhis (1989), Tukmakov (on tie-break), and Judit Polgar (1990), that final OHRA year saw all three Polgar sisters competing in the same event (!), Zsuzsa finished on 12th-15th place, Zsofia was 24th and last.

The Crown tournament (A group) winners at Amsterdam were Karpov (1985), Ljubojevic (1986), Van der Wiel (1987), Korchnoi (1988) and twice Beliavsky (1989, 1990).

Note: During the same years, OHRA also organised some chess events at Brussels, including two invitation supertournaments.

At OHRA Brussels invitation tournaments, Korchnoi (ahead of Spassky) won in 1985, Kasparov (ahead of Korchnoi) won in 1986.

Survey: https://fr.wikipedia.org/wiki/Tournoi_OHRA (in french language)

http://www.xtraconchessopen.dk/ (Official Site)

https://en.wikipedia.org/wiki/Xtracon_Chess_Open (Wikipedia)

The Xtracon Chess Open (formerly the Politiken Cup) is an international chess tournament and the main feature event of the annual Copenhagen Chess Festival. Organized by the Copenhagen Chess Federation (KSU), it was originally set up to give Danish players the opportunity of international experience and title norms. Starting from modest means in 1979, with just 22 contestants, it has grown to become one of the world's largest and most respected open chess tournaments, with numbers of participants rising to 200 in 2003, and nowadays reaching well in excess of 400. 

The tournament has attracted many of the world's strongest grandmasters as well as promising youngsters. Former world champion Vassily Smyslov was among the winners in 1980 and 1986, while other notable winners have included Viktor Korchnoi as clear first in 1996 at the age of 65 and Nigel Short in 2006. At the Politiken Cup in 2003, Magnus Carlsen achieved his third and final IM norm. 

The early editions were held in Copenhagen and its suburbs, before moving to Helsingør. The tournament has always taken the format of a large "Open", accessible to both titled and non-titled players, except in 1983, when there was an invite-only, all-play-all Grandmaster event and a subsidiary Open tournament aimed at International Master level.

Double winning at Politiken Cup in Copenhagen (Open, swiss system) and at Sigeman & Co. in Malmö (Invitation Tournament, round robin) << the same year within one month >>, both won as clear first! A unique Scandinavian summer :))

Viktor Korchnoi (1996 at age of 65)

From 1979 to 2015, the main sponsor was the Danish daily newspaper Politiken, but new arrangements have been announced for 2016–2018. The main sponsor is now Xtracon A/S, a Danish IT company with a chess playing owner. Accordingly, the tournament has been renamed to reflect the change, although it is anticipated that the format will remain broadly the same.

The early editions were held in Copenhagen and its suburbs, before moving to Helsingør. The tournament has always taken the format of a large "Open", accessible to both titled and non-titled players, except in 1983, when there was an invite-only, all-play-all Grandmaster event and a subsidiary Open tournament aimed at International Master level.

In later years the tournament has taken place during July/August, over 10 rounds, at the Konventum, a convention centre and resort set in the scenic surroundings of Helsingør.

http://www.qatarmastersopen.com/ (Official Site, expired)

https://en.wikipedia.org/wiki/Qatar_Masters_Open (Wikipedia, prize funds and winners)

Yu Yangyi from China was clear first above 2./3. Giri, Kramnik in the inaugural edition of 2014.

World Chess Champion Magnus Carlsen won the the second (and latest) Qatar Masters Open in Doha after defeating defending tournament champion Yu Yangyi 2-0 in a speed tie-break. They had tied on 7/9. The field included four top ten players (Carlsen, Kramnik, Giri, and So) plus Karjakin.

https://www.reykjavikopen.com/ (Official Site)

https://en.wikipedia.org/wiki/Reykjavik_Open (Wikipedia)

The Reykjavik Open is an annual chess tournament that takes place in the capital city of Iceland. It was held every two years up to 2008, since then it runs annually. The first edition was held in 1964 and was won by Mikhail Tal with a score of 12.5 points out of 13. The tournament is currently played with the swiss system, while from 1964 to 1980 (biannually) and again in 1992 it was a round-robin tournament. The first Open of the series was won by Lev Alburt as clear first in 1982. (Wikipedia)

Note:

There have been several (further) strong international invitation tournaments at Reykjavik, which are not part of the traditional and numbered series.

In 1972, Reykjavik hosted the World Chess Championship between Boris Spassky (USSR) and Bobby Fischer (USA), also known as "Match of the Century".

http://www.rilton.se/ (Official Site)

http://www.rilton.se/historia.html (List of winners, scroll down)

https://sv.wikipedia.org/wiki/Rilton_Cup (Wikipedia in swedish)

https://pl.wikipedia.org/wiki/Rilton_Cup (Wikipedia in polish, all winners)

(No Wikipedia english entry so far)

Stockholm 1971:

One day, an envelope arrived at the doors of the organizers of the local chess tournament, Stockholm Open. In the envelope there was money — and a note: "Make a strong tournament!"

The event's namesake Dr. Tore Rilton, who died in 1983, wanted the new tournament to become an opportunity for young Swedish talents to challenge strong masters from abroad.  The story about Rilton Cup and its donator: http://chessbase.in/news/rilton-preview/ (ChessBase India).

In 1971/72, IM (then) Jan Timman won the inaugural event above clear second Walter Browne, the beginning of an annual series played over New Year with a rich national and international tradition. Legendary Vasily Smyslov, Viktor Korchnoi (unbeaten as =5^th in 2003/2004), or Mark Taimanov participated, too.

In 2017/18, the Rilton Cup and the Rilton Tournaments set a new participants record in its 47 year long history: In total the three groups, Rilton Cup (126 players, among them 25 GMs), Rilton Elo and Rilton 1800, gathered 362 participants.

Stockholm's Chess Federation and the Rilton Committee are working continuously to create to create an even more attractive tournament for the world's elite and chess lovers of all levels. Every player is portrayed over the board with a professional photo during the event and covered on the official website.

Sharjah is the third largest and third most populous city in the United Arab Emirates, part of the Dubai-Sharjah-Ajman metropolitan area, and located along the southern coast of the Persian Gulf.

Sharjah Chess & Cultural Club

The Sharjah Cultural and Chess Club (Sharjah Hall) was established by Sheikh Dr. Sultan bin Ahmed Al Qasimi, the ruler of Sharjah, and was officially opened on March 28, 2013. The Sharjah Chess Club covers an area of 34,000 cubic feet, including the main hall which can accommodate up to 500 players. Besides two huge playing areas there are many class rooms, library, VIP room, regional FIDE office etc. One can find here all possible modern equipment and devises invented in the chess world.

Sharjah Masters International Chess Championship is organised under the patronage of H.H. Sheikh Dr. Sultan bin Mohammad Al Qasimi, Supreme Council Member and Ruler of Sharjah and held at Sharjah Chess & Culture Club.

The first Sharjah Masters took place in March 2017. Wang Hao edged out Adhiban, Kravtsiv, Kryvoruchko, Sethuraman and Salem on tie-break. 17 year old Iranian GM Parham Maghsoodloo won the second Sharjah Masters in April 2018 a point clear of Eltaj Safarli and Wang Hao.

Note: The city of Sharjah also hosted a FIDE GP in 2017.

Played in swiss system since the mid-1940s, at various venues in the United States.

http://www.uschess.org/tournaments/2017/usopen/ (Official Site)

https://en.wikipedia.org/wiki/U.S._Open_Chess_Championship (Wikipedia)

U.S. Open *1900 - www.chessdiagonals.ch

The Swiss System was used for the first time (after the first two rounds were paired by lot) to determine qualifiers for the various final sections at the U.S. Open in 1946.

Beginning with the U.S. Open in 1947, the Swiss System would be used for the entire tournament and the number of players began to grow. This helped solve the scheduling problems which had plagued previous Open tournaments, when two or three games would have to be played every day for an extended period.

Held mainly in Philapelphia, early editions in New York, later sometimes also in Arlington or other U.S. cities.

http://chessevents.com/worldopen/ (Official Site)

http://chessevents.com/worldopen/world-open-winners/ (List of winners)

https://en.wikipedia.org/wiki/World_Open_chess_tournament (Wikipedia)

The World Open is usually played in the first week of July, sometimes beginning at the end of June. All editions have been organized by the Continental Chess Association.

The 1986 edition in Philadelphia had as many as 1507 participants (all sections together), arguably a world record for a chess tournament. Nick De Firmian won the World Open of 1986 outright and took the first prize of $21,930 at that time supposed to be a record for a swiss system tournament.

Classical chess, annually recurring individual international Open Festivals (swiss system),
present, a selection of the most important series in status and strength

U.S. Open Chess Championships (Open, played annually at various venues) since 1900 without any break!, Reykjavik (Open, at the beginning up and including 1980 and once again in 1992 a biannual international invitation tournament) since 1964, World Open (most often in Philadelphia, sometimes in New York and other U.S. cities) since 1973, Politiken-Cup / Xtracon Chess Open (with renaming in 2016), Copenhagen, Helsingor et al. since 1979, Cappelle-la-Grande (Open), France since 1985, Isle of Man Open (IoM), originally under the patronat of "Monarch Assurance", annually played in Port Erin from 1992 to 2007, after a seven-year break, now relocated in Douglas as "PokerStars" in 2014, and after another extensive relaunch in 2016 labelled as "Chess.com", Dubai Open (Sheikh Rashid Bin Hamdan Al Maktoum Cup) since 1999, Moscow, Aeroflot Open from 2002-2012 (rapid and blitz edition in 2013, no edition in 2014), and again since 2015, Gibraltar Chess Congress (Open) since 2003 in Catalan Bay (span. La Caleta), initially sponsored by Gibtelecom, since 2011 by Tradewise, Las Vegas (for the first two editions) and Atlantic City, Millionaire Chess (Open) launched in 2014, or Qatar Masters (Open) in Doha launched in 2014

Note: Hastings (first invitation tournament in 1895), is today played as an Open Festival using the swiss system since 2005/06 (after one year with knock-out modus). Hastings International Chess Congress welcomed Tradewise Insurance Services as a new sponsor since the edition of 2015/16, in conjunction with Hastings Borough Council and the English Chess Federation. The traditional Sarajevo (Bosna), starting in 1957 with a ten-year break due to Balkan conflicts, is today played as an Open Festival since 2010

Survey in alphabetical order of about 50 annually recurring Open Festivals in classical chess: 

Abu Dhabi Chess Festival, Open
Al-Ain Chess Classic, Open
Andorra Open, in La Massana
Bad Homburg, “Rhein-Main-Open”
Bad Wörishofen, ChessOrg Open
Baku, Open
Bangkok, BCC Bangkok Open
Barcelona, “Open de Sants, Hostafrancs i La Bordeta”
Basel (Riehen), Schachfestival Neujahrs-Open (ex Hilton)
since 1948 Belgrade Trophy, Open
since 1968 Biel Master Tournament, Open
Bratto, Open
Bunratty Masters, Open
since 1956 Canadian Open, at various venues
Capo d'Orso, Porto Mannu Open in Palau, Sardinia
Cappelle-la-Grande, Open
Chicago Open, in Wheeling, Illinois
Copenhagen, Helsingor et al. Xtracon Open (former “Politiken-Cup”), Open
Dehli, Open
Dresden, “ZMDI Festival”, Open
Dubai, “Sheikh Rashid Bin Hamdan Al Maktoum Cup”, Open
Gibraltar, “Tradewise Chess Festival”, Open
Guernsey Chess Festival, Open
since 1963 Groningen Chess Festival, Open
since 1920/21 (1895 Summer Congress) Hastings Chess Congress, Open
Isle of Man  (IoM), “Chess.com Isle of Man International”, in Douglas, 
                       (originally “Monarch Assurance” in Port Erin), Open
Karlsruhe, “Grenke Chess Open” (since 2016 following Deizisau, “Neckar-Open”)
Doha, “Qatar Masters”, Open
Kolkata (Calcutta), Open (successor of Goodricke)
Kuala Lumpur, “Malaysia Open”
Las Vegas (MC1 & MC2), Atlantic City (MC3), “Millionaire Chess” Open
Liechtenstein Open, in Mauren, Triesen et al. (1983-2014, relaunch possible)
Malta Open, in Sliema
since 1960 Mar del Plata, Open
Mérida, Yucatán (Torre Repetto Mem), Open
Metz, Open
Moscow, Open
Minsk, Open
National Open, in Las Vegas, Nevada et al.
North American Open, in Las Vegas, Nevada
Philadelphia Open, Pennsylvania
Pardubice, “Czech Open”
since 1964 Reykjavik, Open
San Sebastian, “Donostia”, Open
since 1957 Sarajevo, “Bosna”, Open
Sharjah Masters, Open
Skopje, Macedonia “Karpos Open”
St. Petersburg (Chigorin Mem), Open
since 1971/72 Stockholm, “Rilton-Cup”, Open
Trieste, Open
since 1900 U.S. Open, at various venues
Vancouver (Keres Mem), Open
Vienna Open (mostly in bi-annual rhythms)
Vlissingen, “Hogeschool Zeeland”, Open
Voronezh Master (Alekhine Mem), Open
since 1973 World Open, at various venues
Zürich Weihnachts-Open (ex Nova-Park)

Sincere apologies to anyone whom I have unintentionally omitted to mention

From a technical point of view, some open tournaments revealed an incredible strength (number of grandmasters participating), but lacked somehow of the same status / prestige  as a closed invitation tournament. Maybe this will change in near future. In 2015, for the first time ever since 1971, Boris Spassky, co-winning at the Canadian Open Chess Championship, held that year in Vancouver, a reigning World Chess Champion participated again in an open tournament (swiss system instead of round robin): Magnus Carlsen, winning at the Qatar Masters in Doha.

From the absolute top-level players, Viktor Korchnoi had the biggest impact, the broadest range of won Superopen Tournaments, followed by Hikaru Nakamura at relatively young age (many strong, but not that much internationally mixed Open in the USA, plus an epic record at Gibraltar), rivalled maybe by Nigel Short and Tony Miles (many of moderate strength), surprising Vlastimil Hort, and several GMs from the United States, of course. If you do consider all Open Festivals with titled players competing, then Sergei Tiviakov is a contender for achieving the most wins in different international swiss system tournaments, above pure local level.

Most of the Superopen are divided into different sections for players of all level 

==> There are hundreds of fascinating local Open Chess Events and Festivals !!

Watch out in your area 😉

Classical chess, annually recurring individual international Open Festivals (swiss system),
past, a selection of the most important series in status and strength

Lone Pine, California, formally titled the Louis D. Statham Masters (strong international Open 1971-1981 with a semi-invitational character, less than hundred players per edition), Lugano, Switzerland (strong International Open 1976-1989, in the 1980 years extremely tough mixed in countries, gender and age of competitors and regularly with top ten players), London Lloyds Bank (strong international Open 1977-1994, many British players), New York Open (strong international Open 1981-2000, no edition in 1982 and 1999, many American players, biggest price money), Berlin Summer (large international Open 1983-1998, many German players, about 400 players in one field), as the arguably five most prominent past series of Chess Open Festivals, among various other cancelled tournaments (Aosta Valley Open in Saint Vincent, Bled Open, Liechtenstein Open, etc.) 

Special, large and strong Swiss system in classical chess:

GMA World Cup Open series 1988-1990
in Belgrad, Moscow, Palma de Mallorca and Moscow (final)

FIDE Interzonal played in a swiss system
in Manila 1990, and in Biel 1993

plus Junior, Senior, and team competitions

Peter Leko explained that the Isle of Man (IoM) Open 2016 was his first open with a classical time control since 1992 (!), Sydney Open in Australia when he was 13 years.

Leko who finished with 5.5/9 at IoM in 2016 said he wants to play more after his relative inactivity over the last two years (that means, he did no longer got invitations after dropping out of the top ten, top twenty in the Elo list and losing his youth bonus).

Leko also said he has to figure out a style that will work in Opens. That’s really a good idea :)

More and more top-level Grandmasters are beginning to take part in Opens and sometimes the very same players win those events, too.

Carlsen triumphed in Qatar and at Isle of Man, Nakamura won Gibraltar thrice in a row (in total four wins).

On this topic, compare the essay from WGM Alina L’Ami, IoM 2016 in ChessBase:

https://en.chessbase.com/post/looking-back-at-the-isle-of-man-1-2

https://en.chessbase.com/post/looking-back-at-the-isle-of-man-2-2

Open Chess Tournaments or When your meal depends on your next move..

The gap (loss) of a few dozen rating points can make the difference between regular invitations to closed supertournaments and “banishment” to the chancier and less rewarding world of the Open chess circuit:

Globetrotter Vladimir Epishin, is an example of a grandmaster who could claim at the highest level only for a few years, the fate of so many professional chess players just one step beyond the very best. He was a regular top-twenty player in the mid-1990s, who peaked as clear number ten of the world in 1994 (January-June list), but soon afterwards disappeared from the radar of the very best, dropped out of the top hundred (there are plenty strong players today), remaining a very busy Open participant: A real chess professional - who has to win prizes to eat and pay mortgages or rent.

Think also of traveller Sergei Tiviakov, winner of the European Individual Chess Championship in 2008 and always dangerous for anyone, or Bartosz Soćko, the Polish player is one of the most busiest professionals today, or Lithuanian world voyageur Eduardas Rozentalis, there aren't that many countries in which he hasn't played a competitive game, or multiple British Rapid Chess Champion Mark Hebden, who also seems to be playing non-stop following the chess winds seeking a weekly wage, or from Hungary, veteran Iván Faragó, supposed to have the second largest number of higher class games, after Viktor Korchnoi.

No guaranteed prize money (except you got 'conditions') plus potential to lose face and a ton of Elo points if they have a couple of drawn games against lower rated participants: That's why top ten, top five players didn't often play in open tournaments (swiss system).

Rare empirical exceptions of fearless top-level chess prominence, playing as well even during their heyday frequently in Open tournaments (swiss system, non predictable opponents contrary to a closed round robin, no chances for drawing masters), are especially Korchnoi and Nakamura (i.e. Short, Miles and others accelerated to play in international Open when they were no longer ranked in the top ten, top twenty of the world, or participated primarily in Open in their youth years, before they advanced to the absolute elite).

From the absolute top-level players, Viktor Korchnoi had the biggest impact, the broadest range and diversity of Superopen series, followed by Hikaru Nakamura at relatively young age (many strong, but not that much internationally mixed Open in the USA, plus an epic record at Gibraltar), chess Open is his favourite hunting ground, in closed elite tournaments (round robin or knock-out), comparatively, Nakamura seems to be somehow less successful.

Then there are surprising strong Vlastimil Hort (winning or co-winning Lone Pine, U.S. Open, London Lloyds Bank, Berlin Summer, Amsterdam OHRA, plus some less known Open Festivals), the mentioned Nigel Short and Tony Miles (including many tournaments of rather moderate strength), Gyula Sax or Alexei Shirov, as well as many strong American GMs frequently playing and surviving the harsh competition of the large Open chess tournaments in the United States, of course (eg. from Benko to Browne, from Christiansen to Kamsky, from Evans to De Firmian).

From all World Champions, until Carlsen arrived, it is first and foremost Boris Spassky who did play and (co-)won several different Open of note (see the list further below). If you do consider all Open Chess Festivals with titled players participating, then Sergei Tiviakov is a contender for achieving the most wins in different international swiss system tournaments, above pure local club level, yet sometimes, Tiviakov, the traveller, was the only grandmaster in the open field.

Fischer  played in the inaugural edition of the Canadian Open Chess Championship, held at Montreal in 1956 as a thirteen years young teenager, and won the U.S. Open at Cleveland in 1957 (on tie-break above Arthur Bisguier). Later as reigning World Chess Champion, and for twenty years afterwards, he didn’t play any competitive chess game whatsoever.

Karpov  very rarely played in an Open tournament in classical chess during his prime time, and never as a reigning World Champion. He heavily criticized the swiss system, eg. after the IBM-Vienna Open in 1986 with four top ten players, Karpov himself, Korchnoi, Beliavsky, and Spassky (organized in the style of Lone Pine).

Kasparov  did never play an individual international Open tournament (swiss system) in classical chess after becoming a Grandmaster in 1980, the year he won the official FIDE World Junior Chess Championship in Dortmund, played in swiss system.

Kramnik  did not play any individual Open tournament in classical chess after the official FIDE Interzonal tournament in Biel 1993 and the PCA Qualifier (equivalent to FIDE's Interzonal) in Groningen 1993, then both held in swiss system up to the first Qatar Masters, held at Doha in 2014, a span of 21 years! Prior to that, he played for instance at Dortmund Open in 1992 or at Gausdal Troll Masters (Open) in 1992.

Note: Since the 1976 Chess Olympiad in Haifa, Israel, and since the 1989 European Team Chess Championship, also in Haifa, these two major FIDE team events are organised in swiss system, but team events have quite a different character, and there a player can pretty easily avoid to play an opponent (s)he doesn't like, taking a rest day.

Top players entering (and winning) in swiss system formated Open Festivals!

Magnus Carlsen emulates Boris Spassky (1971) and reaps reward at Qatar Open (2015):

Magnus Carlsen’s bold decision to play in an open tournament at Doha, Qatar Masters in 2015, the first reigning male world chess champion to do so since Boris Spassky in 1971, paid off handsomely when the 25-year-old Norwegian won first prize unbeaten on 7/9 with one of his best performances. He tied with Yu Yangyi, then crushed his Chinese rival 2-0 in the speed tie-break.

https://www.theguardian.com/sport/2016/jan/01/magnus-carlsen-emulates-boris-spassky-qatar-open (Leonard Barden)

The Qatar Masters Open took place 19th to 30th December 2015. World Champion Chess Magnus Carlsen heads a stellar field. This was the first appearance by a reigning male World Champion in a Swiss system Open at standard time controls since Boris Spassky played in Vancouver (co-winning wiht Hans Ree) and the Toronto CNE, both in 1971.

Vladimir Kramnik, Anish Giri, Wesley So, Sergey Karjakin, Li Chao, Shakhriyar Mamedyarov, Evgeny Tomashevsky, Pentala Harikrishna, Dmitry Jakovenko Yu Yangyi, Wei Yi, etc. 18 players rated over 2700 Elo and 50 over 2600 Elo compete. Magnus Carlsen won the event after defeating last year's champion Yu Yangyi 2-0 in play-off (blitz, there was no previous rapid). They both had tied on 7/9.

Overview

Four or more top ten players participating in an individual international (non-official) Open chess tournament

Lone Pine, California, Louis D. Statham Masters 1978

The eight edition of the Lone Pine series was the first ever Open (swiss system) with four top ten ranked players:

ex-World Champion Petrosian (#7=), plus Portisch (#3=), Polugaevsky (#7=), and Larsen (#7=). In addition, Timman and Panno from the top twenty FIDE Elo rating list.

Bent Larsen, danish dynamite, won outright.

http://www.chessgames.com/perl/chess.pl?tid=81012

Vienna, IBM-Open 1986

Vienna-IBM 1986 was the first ever Open (swiss system) with two World Champions participating, again four current top ten players of the world (report at the top of this page):

ex-World Champion Karpov (#2), Korchnoi (#6), Beliavsky (#7=), and ex-World Champion Spassky (#9=), followed by Nunn (#top twenty of Elo list January 1986).

Viktor Korchnoi, at age of 55, won on tie-break above shared 1st-2nd Alexander Beliavsky, surpassing Karpov and Spassky.

http://www.nytimes.com/1986/04/08/nyregion/chess-vienna-ibm-contest-won-by-korchnoi-and-belyavsky.html (Robert Byrne)

Doha, Qatar Masters 2015

Again four top ten players of the world were competing in an Open at Doha, the second edition of the Qatar Masters 2015:

reigning World Champion Carlsen (#1), ex-World Champion Kramnik (#4), Giri (#8), and So (#10), followed by Karjakin (#12 of Elo list December 2015).

Magnus Carlsen won after speed play-off versus Yu Yangyi from China.

http://theweekinchess.com/chessnews/events/qatar-masters-open-2015

Douglas, Isle of Man Masters 2017

Isle of Man Masters (IoM Open) in Douglas 2017, was the first ever Open with five top ten players and three World Champions:

reigning World Champion Carlsen (#1), ex-World Champion Kramnik (#3), Caruana (#5), ex-World Champion Anand (#7), and Nakamura (#10 of Elo list September 2017).

Magnus Carlsen won as clear first, and proudly presented his girlfriend 💋.

http://theweekinchess.com/chessnews/events/chess.com-iom-masters-2017

Five of the current top ten players competing in an Open tournament (=non-official swiss system), this is a new record! It was the 20th edition of IoM, but the organisers do not number their series.

Open Festivals of major status in classical chess (standard controls), no rapid of blitz, no events in k.o. or a combined format; no FIDE official, qualification or national tournaments, no team competitions, no Junior or Senior

Reigning World Champions (full list)

Spassky: Canadian Open in Vancouver 1971 (together with Hans Ree):
http://chess.ca/canadian-opens-1970-1980#seventyone

Gaprindashvili: Lone Pine, Louis D. Statham Tournament 1977 in a four-way tie at the top (Balashov best on tie-break, Sahovic, Panno, and Gaprindashvili, nine rounds):
http://www.chessgames.com/perl/chess.pl?tid=80958

Carlsen: Qatar Masters (Open) in Doha 2015 (after blitz play-off vs. Yu Yangyi):
http://www.chessgames.com/perl/chess.pl?tid=86789

Carlsen: Isle of Man (Open) in Douglas 2017 (clear first ahead of 2./3. Anand and Nakamura):
http://www.chessgames.com/perl/chess.pl?tid=91213

Non-reigning World Champions (selection)

Fischer: U.S. Open in Cleveland, Ohio 1957 (on tie-break above Arthur Bisguier)

Petrosian: Lone Pine, Louis D. Statham Tournament 1976 as clear first in a seven-round length

Smyslov: Politiken-Cup 1980 (shared) and 1986 (shared); note: Smyslov won also the 6th edition of the Reykjavik (today: Open) series in 1974, but then it has been played as a closed invitation

Spassky: Lloyds Bank Masters 1984 (shared, Nunn best on tie-break in a five-way tie)

Spassky: U.S. Open in Hollywood, Florida 1985 (shared with Seirawan and Benjamin)

Tal: Berlin Summer 1986 (best on tie-break); note: Tal won also the inaugural event of the Reykjavik (today: Open) series in 1964, but then it has been played as a closed invitation

Vierte Ausgabe 1986 in Berlin, 466 Teilnehmer ! (davon 12 GM, Pia Cramling und Computer Mephisto) 

1. Michail Tal (Sieger nach Wertung), IM Nathan Birnboim, Arild Lauvsnes (Norwegen), ua. vor Dizdar, Drasko, Hertneck, Jansa, Velikov, Lengyel. Kindermann, Gheorghiu, Gutman, Rogers, Inkiov, Pia Cramling, Klundt, Radulov, Bellon, King, Spassov, Tringov.  Mephisto-Computer  mit 5.5/9!

Letzte Runde mit GM Velikov vs. GM Tal 0-1, IM Birnboim vs. GM Lengyel 1-0.

Erstmalige Teilnahme eines sowjetischen Spielers: Top-Favorit Ex-Weltmeister Michail Tal gewann, wenn auch knapp (Levente Lengyel hätte Turniersieger werden können mit einen Sieg gegen Nathan Birnboim).

Die Sieger des vorangegangenen Jahres 1985 waren Suba (Feinwertung) und Kortschnoi. Die Serie Berliner Sommer Open startete 1983 unter dem Namen American Summer, Hort als Alleinsieger, 1984 Lobron (mit Hulak und Lein), und wurde jährlich bis und mit 1998 ausgetragen, in den '90er Jahren jedoch ohne Stars.

Note:
Anand won many rapid & blitz and events (frequently in k.o.-format), Fischerrandom and Advanced chess, i.e. he is multiple winner of the Corsican Circuit, at Leon series or the Chess960 Rapid inofficial World Championship in Frankfurt and later in Mainz. In classical chess, Anand was joint winner of the Kolkata Open. Kramnik is a Troll winner, an Open in Gausdal, Norway, and shared winner at Dortmund Open, which is of minor strength compared with the traditional Open series above. Karpov won a Rapid Open in Moscow, Kasparov won a national qualification open tournament in Daugavpils, joint with Igor Ivanov. Carlsen also won an Open in Gausdal, the Bygger'n Masters, Arnold Eikrem Memorial in 2005. As reigning World Chess Champion, he played and won the superstrong Open Festivals in Doha (Qatar Masters) in 2015 and in Douglas (Isle of Man Masters) in 2017; survey above.