Boris Becker, 1985 (17 years, 7 months)
Becker is a German former world No. 1 professional tennis player. He is a six-time major singles champion; including, having been the youngest Wimbledon men's champion when he was 17. He has won 3 Wimbledon titles. He also won 13 Masters Series titles, five elite indoor titles (three ATP Tour Finals, a WCT Finals, and a Grand Slam Cup).