American Serena Williams has been knocked out of the 2012 Australian Open, in a shock upset by the unseeded Ekaterina Makarova.

The 2010 winner of the tournament made 37 unforced errors as the 56th-ranked Makarova won 6-2, 6-3 in 82 minutes. The result ended Williams' 17-match Australian Open-winning streak. Her last defeat in Melbourne came in the quarterfinals against Serbian Jelena Jankovic in 2008.

I don't know what to say. It's an amazing feeling, said Makarova, the 23-year-old Russian left-hander. She's an unbelievable player. It's really tough to play against her so I'm really happy I finished it, she added.

The 30-year-old Williams, seeded 12th, saved five set points before dropping the opening set and three match points on her serve in the final game.

I can't even describe how I served to be honest, it wasn't good though, Williams said.

Meanwhile, Makarova will meet the winner of the match between Maria Sharapova and Sabine Lisicki, in the quarter-finals. This is her first quarter-final appearance at a Grand Slam.

Check out photographs of the match here...

Ekaterina Makarova of Russia hits a return to Serena Williams of the U.S. during their women039s singles match at the Australian Open tennis tournament
Ekaterina Makarova of Russia hits a return to Serena Williams of the U.S. during their women's singles match at the Australian Open tennis tournament Reuters
Ekaterina Makarova of Russia celebrates defeating Serena Williams of the U.S. during their women039s singles match at the Australian Open tennis tournament
Ekaterina Makarova of Russia celebrates defeating Serena Williams of the U.S. during their women's singles match at the Australian Open tennis tournament Reuters
Serena Williams of the U.S. throws her racquet during her women039s singles match against Ekaterina Makarova of Russia at the Australian Open tennis tournament
Serena Williams of the U.S. throws her racquet during her women's singles match against Ekaterina Makarova of Russia at the Australian Open tennis tournament Reuters