Fruhvirtova revels in 'surreal' Australian Open aged just 17
The Czech teenager recovered from a break down in the third set against compatriot Marketa Vondrousova to win 7-5, 2-6, 6-3 and reach the last 16 in Melbourne.
"It feels pretty surreal," she told reporters.
"It's an incredible feeling. I'm just so happy and excited to be able to say: 'Hi second week!'
"I'm still 17. It's my second main-draw appearance in a Grand Slam. I'm through to the second week, last 16, in such a big tournament," said Fruhvirtova, who reached the second round of the US Open on her Grand Slam debut last year.
"I feel good and I'm excited to be playing the next match here."
The teenager faces Donna Vekic of Croatia next.
Fruhvirtova and Vondrousova both suffered physically at the end of a gruelling afternoon encounter that lasted 2hr 17min.
Vondrousova had knocked out second seed Ons Jabeur in the previous round in an attritional match that did not finish till past 1am and she called a timeout for the trainer near the end.
Fruhvirtova, ranked 82 and four places higher than her opponent, needed no second invitation to pounce.
She went on a tear, winning 11 of 12 points to earn triple break points at 4-3.
She needed only two and stayed composed to close out the match with ease.
In a wide-open bottom half of the draw, Fruhvirtova will fancy her chances against the 64th-ranked Vekic On Monday for a place in the quarter-finals.
Vekic beat Spain's Nuria Parrizas Diaz 6-2, 6-2.
