What were the longest professional men’s and women’s grand slam tennis matches? 
 
Men’s: Fabrice Santoro versus Arnaud Clément at the 2004 French Open, it lasted 6 hours and 33 minutes on May 24, 2004. Santoro won the match 6-4, 6-3, 6-7(5), 3-6, 16-14.

Women’s: 2005 Wimbledon Final. V. Williams d. L. Davenport 4-6, 7-6(4), 9-7.
Eventually, after 2 hours and 45 minutes, in the longest Women's Wimbledon Final ever, Venus was the last woman standing.