A tearful Roger Federer powered home to beat Marin Cilic in five riveting sets to win his sixth Australian Open and 20th Grand Slam title on Sunday.

The Swiss defending champion dropped his only sets of the tournament before completing a 6-2, 6-7 (5/7), 6-3, 3-6, 6-1 win over the sixth seeded Croatian in 3hr 3min.

Federer, playing in his 30th Grand Slam final, joined Novak Djokovic and Australian great Roy Emerson as joint top for the most Australian Open men's titles.

"I’m so happy it’s unbelievable. This is a dream come true, the fairytale continues for me," Federer said at the presentation.

"After the great year last year, it’s incredible," the 36-year-old added as he broke down in tears.

Federer added to his already imposing win-loss record in Melbourne and is now 94-13. His overall his Grand Slam mark stands at 332-52.

"It was an amazing journey to come to the final. It could have been the best two weeks of my life, but Roger played a great fifth set," Cilic said.

"I want to thank my team, you’re unbelievable. We worked hard for this  year, hopefully we will lift these trophies in the future."