is a Swiss professional tennis player who is ranked world No. 4 in men's singles tennis by the Association of Tennis Professionals (ATP). He has won 20 Grand Slam singles titles—tied for the most in history for a male player with Rafael Nadal—and has held the world No. 1 spot in the ATP rankings for a record total of 310 weeks and was the year-end No. 1 five times, including four consecutive. Federer, who turned professional in 1998, was continuously ranked in the top 10 from October 2002 to November 2016.