#3 Mats Wilander (17 years, 293 days)
To this date, Mats Wilander remains the only men's player to have won four Grand Slam titles before turning 20.
He won his first title in 1982 at the age of 17 as an unseeded player by defeating Guillermo Vilas at the French Open in 4 sets.
He won a total of 7 Grand Slam titles before retiring at the age of 32. He never managed to win Wimbledon, despite winning the Australian Open, which was played on grass courts at the time, thrice.
What is the foot injury that has troubled Rafael Nadal over the years? Check here
Edited by Arvind Sriram