Australian Open champion Sofia Kenin fought back from match point down to defeat world No 197 Jaqueline Cristian in epic fashion at the Lyon Open.

The world No 5 lost the first set before clawing her way through a nail-biting climax to win 6-7 (5) 7-5 6-4 in two hours and 32 minutes and advance through to the quarter-finals.

After an opening set where the pair shared two breaks apiece, it was Cristian who showed the legs to grind out the decisive points at the end of the tie-break and take a surprise lead.

And the 21-year-old Romanian continued to outplay Kenin in the second set as she broke the American to put herself in a position where she was serving for the match at 5-4.

But the No 1 seed showed the spirit of a Grand Slam winner as she dug her heels in, saving match point and breaking to level things up.

After holding her serve to lead 6-5, Kenin spurned three set point opportunities before eventually breaking as the match headed to a decider.

Seven games into the crucial third set both players had held their nerve, before the champion from Melbourne broke Cristian to lead 5-3 and clinch what appeared to be the decisive break of the match.

But somehow Cristian came roaring back immediately to level things up as the match took yet another twist.

Quite incredibly, though, the drama did not stop there as Kenin caught her opponent cold to secure a third break in as many games and seal victory in front of a captivated crowd.

After the match, Kenin said: "She was playing with no pressure. She qualified, so I knew she would come out playing some really good tennis.

"Obviously I didn't feel my game that well - I was pretty frustrated the whole match, I couldn't find my rhythm, but I just tried to fight through. I got the win - it's a relief and I'm happy."

The American will now face France's Océane Dodin on Friday for a place in the last four.