2021 French Open – Men's singles

Novak Djokovic defeated Stefanos Tsitsipas in the final, 6–7^(6–8), 2–6, 6–3, 6–2, 6–4 to win the men's singles tennis title at the 2021 French Open. It was his second French Open title and 19th major title overall. Djokovic became the first man to achieve the double career Grand Slam in the Open Era, and the first player in the Open Era to win a major after coming back from two-sets-to-love down in two matches during the same major. Tsitsipas was the first Greek to reach a major final. It also marked the second consecutive year a man trailed by two sets in a major final yet rallied to win, following Dominic Thiem's victory at the 2020 US Open. It was the first time since 2004 that the final went to five sets; on that occasion, Gastón Gaudio also came from two sets down to win the title.

Rafael Nadal was the four-time defending champion, but lost to Djokovic in the semifinals. Nadal's defeat marked only his third loss out of 108 French Open matches, including his first loss in 14 semifinal appearances at the tournament. Djokovic became the only man to defeat Nadal twice at the French Open, and the only man to win the title after defeating him. It was the pair's record-extending 58th meeting.

Djokovic and Daniil Medvedev were in contention for the world No. 1 ranking; Djokovic retained the top position after Medvedev lost in the quarterfinals.

Nadal and Roger Federer were attempting to win a record-breaking 21st major title and become the outright leader in the men's singles major tally. Federer, like Djokovic, was attempting to become the first man in the Open Era to achieve the double career Grand Slam; this would be the 2009 champion's last French Open appearance. This was the only time that the Big Three, the three most successful men's singles major champions of all time, were in the same half of the draw at a major.

For the first time in the Open Era, no French players reached the third round. Thiem's first-round defeat guaranteed a new French Open finalist from the bottom half of the draw; Tsitsipas ultimately emerged as that finalist.

This marked the French Open debut of future two-time champion Carlos Alcaraz. He was the youngest player to win a match at the French Open since Djokovic in 2005 , and the youngest to reach the third round since Andrei Medvedev in 1992.