Mats Arne Olof Wilander is a Swedish former professional tennis player. He was ranked as the world No. 1 in men's singles by the Association of Tennis Professionals (ATP) for 20 weeks, including as the year-end No. 1 in 1988. Wilander won 33 career singles titles, including seven majors (three each at the French Open and Australian Open, and one at the US Open), and seven career doubles titles, including a major in men's doubles at Wimbledon.
Wilander's breakthrough came suddenly and unexpectedly when he won the 1982 French Open at the age of 17. Wilander won his fourth major singles title at the age of 20, the youngest man in history to have achieved the feat. In 1988, he won three of the four singles majors to finish the year ranked as the world No. 1. Wilander also won eight Grand Prix Super Series titles (1983–88), the precursors to the current ATP Masters 1000 tournaments. He was also a driving force behind Sweden's run of seven consecutive Davis Cup finals from 1983 to 1989, and three titles in 1984, 1985, and 1987.