Björn Rune Borg (Swedish pronunciation: [ˈbjœːɳ ˈbɔrj] (listen); born 6 June 1956) is a Swedish former world No. 1 tennis player. Between 1974 and 1981, he became the first man in the Open Era to win 11 Grand Slam singles titles (six at the French Open and five consecutively at Wimbledon), but he never won the US Open despite four finals appearances. He is the first male player to win five Wimbledon titles in the Open Era, as well as the only Swedish tennis player, male or female, to win more than 10 Grand Slams.

Borg won four consecutive French Open titles (1978–81) and is 6–0 in French Open finals. He is one of two male players, along with Roger Federer, to appear in French Open and Wimbledon finals for four consecutive years (1978–81) and the only man to win both of them in three consecutive years (1978–80).

He was the first male player since 1886 to appear in six consecutive Wimbledon finals, a record surpassed by Federer's seven consecutive Wimbledon finals (2003–09). Borg is the first male player to appear in the French Open, Wimbledon and US Open finals in the same year three times (1978, 1980–81), a record surpassed by Federer who achieved the same in four consecutive years (2006–09). He won three major titles without dropping a set in the entire tournament.

He also won three year-end championships and 16 Grand Prix Super Series titles. Overall, he set numerous records that still stand. Borg was the first player to win six French Open singles titles. He was ATP Player of the Year from 1976 to 1980, finished the year as

No. 1 player in the world in the ATP rankings in 1979 and 1980 and was ITF World Champion from 1978 to 1980.

A teenage sensation at the start of his career, Borg experienced unprecedented stardom and consistent success that helped propel the rising popularity of tennis during the 1970s. As a result, the professional tour became more lucrative, and in 1979, he was the first player to earn more than one million dollars in prize money in a single season. He also made millions in endorsements throughout his career.