During the Sinquefield Cup in September 2022, a controversy arose involving the chess grandmasters Magnus Carlsen, then world champion, and Hans Niemann. Carlsen, after being upset in their third-round matchup, dropped out of the tournament. Many commentators, most vocally grandmaster Hikaru Nakamura, interpreted his withdrawal as tacitly accusing Niemann of having cheated. In their next encounter in an online tournament, Carlsen abruptly resigned after one move, seemingly doubling down on his insinuation. The controversy became the most serious scandal about cheating allegations in chess in years, and it garnered significant attention in the news media worldwide.

After the fifth round of the Sinquefield Cup, Niemann gave a lengthy interview addressing the controversy, in which he admitted to cheating in online chess in the past, but denied cheating in the game with Carlsen or in any over-the-board game. Three weeks later, Carlsen released a statement saying that Niemann's behavior during their Sinquefield Cup game, taken together with earlier suspicions, had persuaded him to withdraw from the tournament. Carlsen expressed the belief that Niemann had cheated more often and more recently than he had publicly admitted.

Chess.com removed Niemann from their platform in the days after Carlsen's withdrawal from the Sinquefield Cup. FIDE, the international chess governing body, rebuked Carlsen for his actions but at the same time acknowledged his concerns about cheating in Chess. FIDE later announced an investigation into Carlsen's claims of cheating and Niemann's response. Chess.com released an interim report summarizing their evaluation of Niemann's games and their estimation of his online cheating on their platform. Many chess players and journalists commented on the issue, some supporting Carlsen's suspicions in one way or another, others criticizing him for his tournament withdrawal and for making allegations without providing any evidence. Most top players expressed the view that Niemann had not cheated in the game against Carlsen, partly also criticizing Carlsen's play in the game. Most commentators expressed their desire for strict and consistent cheating controls in chess tournaments.

In October2022, Niemann filed a lawsuit against Carlsen, his company Play Magnus Group, Chess.com, Chess.com's Chief Chess Officer Daniel Rensch, and Nakamura for defamation and unlawful collusion. The complaint claimed that statements in the Chess.com report had falsely accused Niemann of a more extensive history of cheating in the past than he had publicly admitted, and that those statements were part of a malicious conspiracy to defame Niemann. The antitrust claims in the lawsuit were dismissed in June2023.

In August2023, Chess.com announced that all parties involved in the lawsuit had settled; Chess.com reinstated Niemann on their platform and Carlsen admitted that there was no determinative evidence that Niemann had cheated in their Sinquefield Cup game. He promised to play against him should they be paired. That December, FIDE fined Carlsen 10,000 euros for his withdrawal from the Sinquefield Cup, but acquitted him of all charges related to his unsubstantiated allegations against Niemann.

Background In 2022, Carlsen was the No. 1 rated player in history and World Chess Champion. In July 2022, Carlsen announced he would not defend his World Chess Championship title against Ian Nepomniachtchi, while affirming his desire to participate in tournaments and continue playing professional chess. At this time, Niemann stood in the top 10 of the world's juniors in chess and top 50 players overall. Over the previous three years, he had played a large number of games, and his Elo rating had risen swiftly, including a jump from 2500 to 2600 in only three months. This rapid rise had attracted attention from commentators.

In August 2022, Niemann and Carlsen both competed in the FTX Crypto Cup, an in-person rapid event hosted by Chess24 in Miami. On August 16, Niemann faced Carlsen in a four-game match, and beat him in the first game with the black pieces. After the game, when asked for a post-game interview, he said only "Chess speaks for itself." He proceeded to lose the subsequent three games against Carlsen.

In September, Carlsen participated as a wildcard in the 2022 Sinquefield Cup, an over-the-board tournament with classical time control and part of the Grand Chess Tour. Entering the tournament, he had a 53-game unbeaten streak in classical games which determine the FIDE world rankings.

Sinquefield Cup

On September 4, 2022, in the third round of the Sinquefield Cup, Niemann defeated Carlsen with the black pieces, playing the Nimzo-Indian Defense. His live rating surpassed 2700 for the first time with this win. Slate described the result as a "shocking upset" for Carlsen, ending his unbeaten streak to a player with a far lower rating, and in a game where he had the first-move advantage.

Location: St. Louis Missouri, U.S. Date: September 4, 2022 White: Carlsen, Magnus Black: Niemann, Hans E20: Nimzo-Indian, Romanishin–Kasparov–Steiner system Result: Moves: 57

1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.g3 0-0 5.Bg2 d5 6.a3 Bxc3+ 7.bxc3 dxc4 8.Nf3 c5 9.0-0 cxd4 10.Qxd4 Nc6 11.Qxc4 e5 12.Bg5 h6 13.Rfd1 Be6 14.Rxd8 Bxc4 15.Rxa8 Rxa8 16.Bxf6 gxf6 17.Kf1 Rd8 18.Ke1 Na5 19.Rd1 Rc8 20.Nd2 Be6 21.c4 Bxc4 22.Nxc4 Rxc4 23.Rd8+ Kg7 24.Bd5 Rc7 25.Ra8 a6 26.Rb8 f5 27.Re8 e4 28.g4 Rc5 29.Ba2 Nc4 30.a4 () Nd6 31.Re7 fxg4 32.Rd7 e3 33.fxe3 Ne4 34.Kf1 Rc1+ 35.Kg2 Rc2 36.Bxf7 Rxe2+ 37.Kg1 Re1+ 38.Kg2 Re2+ 39.Kg1 Kf6 40.Bd5 Rd2 41.Rf7+ Kg6 42.Rd7 Ng5 43.Bf7+ Kf5 44.Rxd2 Nf3+ 45.Kg2 Nxd2 46.a5 Ke5 47.Kg3 Nf1+ 48.Kf2 Nxh2 49.e4 Kxe4 50.Be6 Kf4 51.Bc8 Nf3 52.Bxb7 Ne5 53.Bxa6 Nc6 54.Bb7 Nxa5 55.Bd5 h5 56.Bf7 h4 57.Bd5 Ke5 0–1

Carlsen's withdrawal Carlsen withdrew from the tournament the following day, tweeting a simple announcement of his withdrawal alongside a video of José Mourinho saying "I prefer really not to speak. If I speak, I am in big trouble." Carlsen's withdrawal did not formally allege that Niemann had cheated, but the broader community saw his tweet as heavily insinuating an accusation.

This was the first time in Carlsen's career that he had withdrawn from a major event in progress, and the incident was considered "virtually unprecedented" in top-level chess. As he had not played half of his matches in the event, the results from his first three games were annulled from the tournament, disrupting the early standings. Former world champion Garry Kasparov said that Carlsen's withdrawal from the tournament had "no precedent in the past 50 years", and called on Carlsen, who had refrained from comment, to explain his decision. Rampant speculation about the reasoning behind Carlsen's withdrawal on social media fueled the growing controversy. Another former world champion, Anatoly Karpov, added "Carlsen surprisingly played the opening so badly with white that he automatically got into a worse position. Then he showed a strange inability to cope with the difficult situation that had arisen on the board. Comments that White lost without chances are complete nonsense."

Julius Baer Generation Cup

On September 19, 2022, Carlsen was again scheduled to play Niemann in the Julius Baer Generation Cup, an online tournament hosted by chess24 that was part of the Champions Chess Tour. He began the match, made one move against Niemann, then resigned and switched off his webcam.

The resignation prompted confusion and surprise from commentators Tania Sachdev and Péter Lékó. Grandmaster Maurice Ashley tweeted: "This is shocking and disturbing. No one can be happy that this is happening in the chess world. Unbelievable!"

On September 21, after the end of the preliminary rounds of the tournament, Carlsen answered a question from chess24's broadcast of why he forfeited: "Unfortunately, I cannot particularly speak on that, but people can draw their own conclusions, and they certainly have. I have to say I'm very impressed by Niemann's play and I think his mentor Maxim Dlugy must be doing a great job." Carlsen's mention of Dlugy brought to light past accusations against Dlugy of cheating on Chess.com.

On September 25, Carlsen won the tournament after defeating Arjun Erigaisi in the second final match. In his last tournament interview, Carlsen said he would provide a statement on the controversy within days. He added that he "generally [wants] cheating in chess to be dealt with seriously", and it would not be the last time he would address the topic. In a follow-up interview with TV 2's chess broadcast, Carlsen said he would "probably" post a statement on social media and that there were limits on what he could say. He did not state if those limits were for legal reasons. Carlsen stated that he wanted more focus on "fair play" in chess:It has always been a code of honor in the game at the top level that you trust each other. You know it is possible to cheat and probably not get caught, but it is so totally devastating to be caught, so then you trust that the incentives are not big enough for the best to cheat. It may feel like the time is ripe to change that point of view.On September 28, Chess.com provided Vice with internal communications between their staff and Dlugy, revealing that Dlugy had been banned from Chess.com in 2017 and 2020 for cheating in their online tournaments. Dlugy had confessed to repeatedly crowdsourcing moves from his chess academy and using an "outside source". In a statement to Vice, Dlugy criticized Carlsen for implying he was involved in the ongoing controversy, and asserted he would consider legal action against him. Dlugy later posted a statement on his involvement in the controversy, and said he believed lawsuits would follow.

Cheating allegations against Niemann Grandmaster and streamer Hikaru Nakamura said he believed Carlsen had likely suspected Niemann of cheating, claiming that Niemann had previously been banned from Chess.com for cheating in online chess games. Levon Aronian, a grandmaster who was playing in the Sinquefield Cup, initially defended Niemann, stating that most high-level players are "pretty much paranoid" and that young players often draw accusations of cheating after strong play. A week later, Aronian stated that he "really didn't know much about a lot of things" and now finds himself "somewhere in the middle". He added, "I do believe Hans has not been the cleanest person when it comes to online chess." According to an anonymous source cited by the Wall Street Journal, Niemann's poor performance in Miami in August 2022, both at the eight-person FTX Crypto Cup (where Niemann had some strong games but lost every series) and in an informal beachside game against Carlsen, played a role in Carlsen's suspicions. Nakamura agreed that Miami seemed to play a role in Carlsen's thinking, stating that "When you combine (the poor Miami performances) with the long-existing rumors, Carlsen became convinced something was off."

Niemann's denial