When you go into a boxing ring you have no idea how many rounds it will go. What is the longest a boxing match lasted?

Baseball games too. How many innings did the longest ever baseball game go? How many hours did the longest basketball game go? In golf were there ever any games that took more than one "sudden-death" playoff to determine? So far the longest tennis match took over 5 hours to play over 3 days a few years ago and I believe American John Isner was one of the players.