21-year-old, Greek Australian, Thanasi Kokkinakis, ranked 175th in the world, used a great top-spin forehand to wear down the world number one in front of a stunned sellout crowd.
Kokkinakis lost the first set 6-3 before claiming the second by the same score. He screamed and pumped his fists when he won a tie-break for the deciding third set 7-4.
Federer, widely considered the greatest tennis player of all time, graciously smiled and said well done, as he shook Kokkinakis hand at the net.
The best win of Kokkinakis's injury-interrupted career moves him into a round of 32 matchup against Spains, Fernando Verdasco.
From Adelaide, Kokkinakis has long been said to have top ten potential but has been held back by injuries, especially around the shoulder area.