The longest at Wimbledon was the 1989 second round match between Greg Holmes and Terry Witsken in 1989, which took five hours 28 minutes, although arguably the most famous endurance battle was between Pancho Gonzales and Charlie Pasarell in 1969, which took five hours 12 minutes and finished 22-24 1-6 16-14 6-3 11-9 to Gonzales.
BBC: Wimbledon 2010: Epic halted at 59-59 in fifth set