BJORN BORG | Retired at 26: The Swede dominated tennis in the late 70s and early 80s. He abruptly announced his retirement in January 1983 at age 26, a decision generally attributed to burnout. He won the French Open six times and five successive Wimbledon crowns, before losing to his rival John McEnroe in the final of the US Open, a major tournament he never managed to win. Borg learned to play tennis at a very early age, and, by the time he was 13, he was beating Sweden’s top junior players. After retirement, Borg founded a sportswear company in the early 1990s.