John Donald Budge (June 13, 1915 – January 26, 2000) was an American tennis player. He is most famous as the first tennis player — male or female, and still the only American male — to win the Grand Slam, and to win all four Grand Slam events consecutively overall. Budge was the second man to complete the career Grand Slam after Fred Perry, and remains the youngest to achieve the feat. He won ten majors, of which six were Grand Slam events (consecutively, a men's record) and four Pro Slams, the latter achieved on three different surfaces. Budge is considered to have one of the best backhands in the history of tennis, with most observers rating it better than that of later player Ken Rosewall.

Budge is also the only man to have achieved the Triple Crown (winning singles, men's doubles and mixed doubles at the same tournament) on three separate occasions (Wimbledon in 1937 and 1938, and the US Championships in 1938), and the only man to have achieved it twice in one year. Budge was the world Number 1 amateur in 1937 and 1938 and world Number 1 professional in 1939, 1940 and 1942.