Germany's Angelique Kerber stunned two-time champion Victoria Azarenka as she swept into the Australian Open semi-finals with her first ever win over the Belarusian on Wednesday.

The seventh seed, who had never gone beyond the fourth round at Melbourne Park before, blasted past the 14th seed 6-3, 7-5 and will play either Chinese qualifier Zhang Shuai or British hope Johanna Konta for a place in the final.

It was a huge upset for the German, who had lost all six previous encounters with Azarenka, including in the final of the Brisbane International this month and an epic three-hour marathon at last year's US Open.

"I can't describe it. I was 0-6 (in their head to head) before I came on court. I said 'Just go for it and beat her'. I'm so happy to beat her for the first time," she said.

"I tried to serve well from the first point and play more aggressive than the last few times I played her. This is incredible feeling to play here on centre court.

"It's amazing to be in the semi-final"

Kerber is a renowned fighter and the quality shone through as she battled back from 2-5 down in the second set against a player who has been in ominous form this season.

Azarenka had lost just 11 games in her four matches prior to meeting Kerber and was seen as the main threat to Serena Williams' relentless march to a 22nd Grand Slam crown.

                  
- Belarusian implodes -

Williams brushed aside Maria Sharapova in her quarter-final and faces Agnieszka Radwanska on Thursday for a place in the decider.

But Kerber, who had a stellar 2015, winning four tournaments, second only to Williams' five, had other ideas to become the first German into the last four here since Anke Huber in 1998.

She gave Azarenka the run-around in the opening game, stunning her by getting a break, making the most of consecutive wide forehands.

As sun the blazed down, the 14th seed battled back to score a break point herself on the Kerber serve but the opportunity went begging as she slipped 2-0 behind -- the first time she had been a break down all tournament.

The Azarenka serve was weak, and a double fault handed the German another break in game three after a series of entertaining rallies.

Kerber was playing some sublime tennis with her shot placement perfect, and Azarenka was flummoxed and irritable on court.

But she composed herself to create two break point opportunities in the sixth game, and screamed "C'mon" after a delicate drop shot hauled her back into the match 2-4.

She held serve but her pounding groundstrokes were being returned consistently. Kerber also held and then took the set on her fourth break point when Azarenka snapped a backhand long.

Stung by dropping the first set, Azarenka broke Kerber immediately as the German lost focus, and then held serve to love as they traded blistering groundstrokes, probing for an opening.

Kerber had two break points to make it 3-4 but she couldn't convert, before Azarenka made it 5-3 as the German missed a volley.

But Azarenka lost the plot serving for the set, throwing away three set points and blasting a double fault to gift Kerber a game back.

Kerber broke again to make it 5-5 as Azarenka again failed to bury set points. It cost her dearly with the German storming to victory as the Belarusian imploded.