An inspired Stefanos Tsitsipas roared back from a set down to end Roger Federer's reign as Australian Open champion and reach his first grand slam quarter-final.

Stefanos Tsitsipas was the "happiest man on earth" after dethroning Roger Federer with a sensational Australian Open victory to reach his first grand slam quarter-final.

Tsitsipas produced the best performance of his young career to break new ground, ending Federer's 17-match winning streak at Melbourne Park with a sensational 6-7 (11-13) 7-6 (7-3) 7-5 7-6 (7-5) victory.

The 20-year-old Greek rising star saved all 12 break points he faced and struck 62 winners in an inspired display at a packed Rod Laver Arena on Sunday.

Tsitsipas was understandably emotional after ending Federer's quest to become the first man to win the tournament seven times and claim a 100th singles title of an astonishing career.

The 14th seed said in his on-court interview: "I'm the happiest man on earth right now, I cannot describe it.

"From the beginning, it's very important to keep that mindset when you're on court. To keep going and believe in yourself, believe in your capabilities, what you have, your abilities as a player."

"Roger is a legend of our sport, [I have] so much respect for him. He showed such good tennis over the years, I've been analysing him since the age of six. It was a dream come true just being on Rod Laver facing him. Winning at the end...I cannot describe it."

Tsitsipas showed great composure to recover from a shaky start, having been given a time violation in the first game after failing to beat the serve clock.

He said his battling spirit was key as he fended off a dozen break points - including six set points in the second.

"It's very important to have this aggressive mindset and not think too much of what's going to happen, stay in the moment, play percentage tennis, have first serves in and press from the very beginning." Tsitsipas, who will face Roberto Bautista Agut in the last eight, added.

"I managed to do that, I didn't lose my patience in some of the rallies that we played. That was the key to save those break points. Overall I showed a great fighting spirit and determination."