Roger Federer's bid for a hat-trick of Australian Open titles was crushed as Greece's Stefanos Tsitsipas rose up to floor the Swiss master and become his nation's first Grand Slam quarter-finalist.

In a match pitting the oldest and youngest players left in the men's draw, the 20-year-old Tsitsipas overhauled Federer 6-7, 7-6, 7-5, 7-6 under the lights of Rod Laver Arena, sparking delirium among Greek fans out in force at Melbourne Park.

The 37-year-old Federer, 20 times a Grand Slam champion, will rue his chances, having failed to convert any of the 12 break points he took from Tsitsipas over the course of a riveting clash laden with sparkling shot-making.

Instead, it was Tsitsipas showing a wise head on young shoulders in a final tiebreak of unrelenting tension.

When given a match point after Federer slapped a forehand long, he converted it clinically, forcing a backhand error from the Swiss to announce himself on one of the game's biggest stages.

181229061037367

He raised his arms in triumph and roared at the terraces, bringing tears of joy to his brother's eyes in the players' box.

"There's nothing I can describe, I cannot describe it, I am the happiest man on earth right now," Tsitsipas said in his courtside interview.

"Roger is a legend of our sport, he showed such good tennis over the years. I have been idolising him since I was six.

When the dust settles, Federer will note that he has been upset in the last 16 at the last two Grand Slams, having fallen to unseeded Australian John Millman at the US Open.

"Definitely didn't go the way I expected with the breakpoints," Federer told reporters.

180128125004936

"I have massive regrets tonight. I might not look the part, but I am. I felt like I had to win the second set. Cost me the game tonight."

In the women's draw, fifth-seed Sloane Stephens was knocked out by Anastasia Pavlyuchenkova, the final upset of a day that, in addition to Federer, saw Angelique Kerber, Marin Cilic and Grigor Dimitrov exit the tournament.

Stephens was leading by a set and a break when the Russian world number 44, came powering back, taking the match 6-7, 6-3, 6-3.