John Donald Budge (June 13, 1915 - January 26, 2000) was a champion tennis player who became famous as the first man to win in a single year the four tournaments that the Grand Slam of tennis comprises. He was considered to have the best backhand in the history of tennis, at least until the advent of Ken Rosewall in the 1950s and '60s.

Born in Oakland, California, Budge was the son of a Scottish immigrant and former soccer player. Growing up, he played a variety of sports before taking up tennis. He was tall and slim and his height helped provide what is still considered one of the most powerful serves of all time. He had a graceful, overpowering backhand that he hit with a slight amount of topspin and that, combined with his quickness and his serve, made him the best player of his time. Today, according to Tennis Magazine , he is ranked as one of the 20 greatest players of the 20th century and may well be one of the half-dozen best.

Budge studied at the University of California, Berkeley in late 1933 but left to play tennis with the U.S. Davis Cup auxiliary team. Accustomed to hard-court surfaces in his native California, he had difficulty playing on the grass surfaces in the east. However, a good instructor and hard work changed all that and in 1937 he swept the Wimbledon Championships, winning the singles, the men's doubles title with Gene Mako , and the mixed doubles crown with Alice Marble . He then went on to win the U. S. National singles and the mixed doubles with Sarah Palfrey Fabyan . But he gained the most fame for his match that year against Gottfried von Cramm in the Davis Cup inter-zone finals against Germany. Trailing 1-4 in the final set, he came back to win 8-6. His victory allowed the United States to advance and to then win the Davis Cup for the first time in 12 years. For his efforts, he was named Associated Press Male Athlete of the Year and he became the first tennis player to ever be voted the James E. Sullivan Award as America's top amateur athlete.

In 1938 Budge dominated amateur tennis, defeating John Bromwich in the Australian Open final, Roderick Menzel in the French Open, Henry "Bunny" Austin at the Wimbledon Championships, where he never lost a set, and Gene Mako in the U.S. Open, to become the first person ever to win the Grand Slam in tennis.

Budge turned professional after winning the Grand Slam and thereafter played mostly head-to-head matches. In 1939 he beat the two reigning kings of professional tennis, Ellsworth Vines and Fred Perry, 21 matches to 18 and 18 matches to 11. There was no professional tour in 1940 but in 1941 Budge beat the 48-year-old Bill Tilden, 51 matches to 7. He also won the French professional championship tournament in 1939, as well as the United States championship tournaments in 1940 and 1942. He then joined the United States Air Force to fight in World War II. Unfortunately, a shoulder injury suffered while serving in the military would permanently hinder his playing abilities.

After the War he played on the tour for a few years, mostly against Bobby Riggs, and won the English professional championship in 1947.

After retiring from competition he coached and conducted tennis clinics for children. A gentleman on and off the court he was much in demand for speaking engagements and signed on to lend his name to promote certain lines of sporting goods. He was inducted into the International Tennis Hall of Fame in 1964 and, with the advent of the Open era in tennis, in 1968 he returned to play at Wimbledon in the Veteran's doubles. In 1973, at the age of 58, he and former champion Frank Sedgman teamed up to win the Veteran's doubles championship at Wimbledon before an appreciative crowd.

In December of 1999, Budge was injured in an automobile accident from which he never fully recovered. He died on January 26, 2000 at a nursing home in Scranton, Pennsylvania.

• List of male tennis players