In grand slams, all men's matches are best of five sets, though in other ATP matches it may be best of third sets.
The longest men's match in history and grand slam was in 2010 at Wimbledon in Round 1, John Isner defeated Nicolas Mahut 6-4, 3-6, 6-7 (7-9), 7-6 (7-3), 70-68. The game went over 3 days due to not having enough natural light on day 1 and day 2, making the game span over three days.
Below are the top 5 longest men's tennis match in history:
Below are all the longest men's tennis matches at each grand slam:
Australian Open
5 hours and 53 minutes in the 2012 final, between Novak Djokovic and Rafael Nadal. Djokovic won over five sets, 5-7, 6-4, 6-2, 6-7 (5-7), 7-5.
French Open
6 hours and 33 minutes Round 1 between Fabrice Santoro and Arnaud Clément in 2004. Santoro won 6-4, 6-3, 6-7 (5-7), 3-6, 16-14
Wimbledon
11 hours and 5 minutes in Round 1 between John Isner and. Nicolas Mahut in 2010. Isner won 6-4, 3-6, 6-7 (7-9), 7-6 (7-3), 70-68
US Open
5 hours and 26 minutes semifinal 1992 between Stefan Edberg and. Michael Chang in 1992. Edberg won 6-7 (3-7), 7-5, 7-6 (7-3), 5-7, 6-4