Two-time defending champion John McEnroe defeated Björn Borg in a rematch of the previous year's final, 4–6, 6–2, 6–4, 6–3 to win the men's singles tennis title at the 1981 US Open. It was his third US Open singles title and fourth major singles title overall. It was Borg's fourth runner-up finish at the US Open, his career-best finish at the event. The final would mark the last major appearance of eleven-time major champion Borg, due to his later retirement from the sport. He left the venue before the trophy ceremony, emotionally distraught.
The seeded players are listed below. John McEnroe is the champion; others show the round in which they were eliminated.
John McEnroe (champion)
Björn Borg (finalist)
Ivan Lendl (fourth round) Jimmy Connors (semifinalist)
José Luis Clerc (fourth round) Guillermo Vilas (fourth round) Gene Mayer (fourth round) Eliot Teltscher (quarterfinalist) Roscoe Tanner (quarterfinalist) Brian Teacher (second round).svg/1280px-Flag_of_Australia_(converted).svg.png){kind=small}
Peter McNamara (third round).svg/1280px-Flag_of_South_Africa_(1928-1982).svg.png){kind=small}
Johan Kriek (third round)
Yannick Noah (fourth round)
Wojtek Fibak (first round) Vitas Gerulaitis (semifinalist) Brian Gottfried (fourth round)