Novak Djokovic is a Serbian professional tennis player. He has been ranked as the world No. 1 in men's singles by the Association of Tennis Professionals (ATP) for a record 428 weeks across a record 13 different years, and finished as the year-end No. 1 a record eight times. Djokovic has won a record 24 major men's singles titles, including a record ten Australian Open titles. Overall, he has won 99 singles titles, including a record 72 Big Titles: 24 majors, a record 40 Masters, a record seven year-end championships, and an Olympic gold medal. Djokovic is the only man in tennis history to be the reigning champion of all four majors at once across three different surfaces. In singles, he is the only man to achieve a triple Career Grand Slam, and the only player to complete a Career Golden Masters, a feat he has accomplished twice. Djokovic is the only player in singles to have won all of the Big Titles over the course of his career.