Novak Djokovic is a Serbian professional tennis player. He is currently ranked as world No. 1 by the Association of Tennis Professionals (ATP). Djokovic has been No. 1 for a record total of 343 weeks, and has finished as ATP year-end No. 1 on a joint-record six occasions. He has won an all-time joint record 20 Grand Slam men's singles titles. Overall, he has won 85 ATP singles titles, including a record nine Australian Open titles and a joint record 36 Masters events. Djokovic is the only man in the Open Era to achieve a double career Grand Slam and complete a non-calendar year Grand Slam. He is also the only player to complete the career Golden Masters on the ATP Tour, which he has done twice.