John McEnroe was ranked No. 1 in the world in both singles and doubles tennis in the early 1980s.
McEnroe first reached the top of the singles rankings on March 3, 1980. He became one of the defining players of the era, finishing 1981, 1982, 1983, and 1984 as the year-end No. 1 singles player. His left-handed serve, exceptional touch, and fiery competitive style made him a major rival to Björn Borg, Jimmy Connors, and Ivan Lendl.
His doubles record was equally remarkable. McEnroe reached No. 1 in the doubles rankings and held that position for roughly 270 weeks overall. With longtime partner Peter Fleming, he won seven Grand Slam men’s doubles titles, including four Wimbledon titles and three U.S. Open titles.
The question refers to ranking leadership, not necessarily winning every tournament in both disciplines. McEnroe’s achievement is especially notable because singles and doubles demand different tactical skills, yet he dominated both simultaneously during the early 1980s.