
The three-time quarter-finalist from Slovakia spent just under 90 minutes producing the best of her career. Hantuchova, seeded ninth, fired 27 winners and broke her teenaged opponent six times.
Radwanska made waves with a 2007 US Open fourth-round appearance, where she beat holder Maria Sharapova before losing to Shahar Peer.
Hantuchova will play the winner from Venus Williams and fourth- seeded Serb Ana Ivanovic.
"I feel great," said the winner, who had stalled in the fourth round at Melbourne Park the previous two years.
"I fought for every point even though I didn't start so well. But I believed I could do it. You get to the moment where everything you touch is going in. I want to keep that feeling for as long as possible."