A Grand Slam is when a player wins all four major tennis tournaments (also called the “majors”) in a single year: the Australian Open, the French Open, Wimbledon, and the US Open. Players can also achieve a “Career Grand Slam,” when they win all the majors at any point in their career.. The 2023 Australian Open champion Novak Djokovic has the most Grand Slam titles in the men’s category, while Australian Margaret Court dominated the women’s category. Both players have 24 Grand Slam titles.