#1 John Isner def. Nicolas Mahut, Wimbledon 1st Round, 2010 - 11 hours 5 minutes
Eight years before John Isner took on Kevin Anderson, he took on Nicolas Mahut in what, till-date is the longest ever match in tennis history.
The match spanned over three days and 11 hours with Isner coming out on top. Both the players posed for a photograph with the scoreboard once the match was concluded.
Isner held his nerve at the end to break Mahut's serve and win the match on a day when the 2nd round matches had already begun.
It is difficult to imagine any match breaking this record for a very long time.
Result: John Isner def. Nicolas Mahut 6–4, 3–6, 6–7(7–9), 7–6(7–3), 70–68