The 36-year-old defeated his opponent Croatia's Marin Cilic in five sets 6-2, 6-7, 6-3, 3-6, 6-1 in three hours and three minutes to achieve the milestone in Melbourne this afternoon.
Federer has now drawn level with world No. 14 Novak Djokovic on six Australian titles.
He is also the first man and fourth person in history to hit the twenties in Major singles titles, joining women tennis stars Margaret Court, Serena Williams and Steffi Graf.
