Top-ranked Simona Halep came back after dropping the second set and going down a break in the third to beat Sofia Kenin 6-3, 6-7 (5), 6-4 and move into a third-round match against Venus Williams.
Halep reached the final in Australia last year after saving match points in the third round and again in the semifinals, but lost the championship match to Caroline Wozniacki.
She ended a run of three runner-up finishes at the majors by winning the French Open in her following trip to a Grand Slam event.
Kenin went on a roll in the third set and was leading 4-2 but gave Halep a break-point chance with a double-fault and allowed the Romanian to get back on serve when she hit a wayward forehand.
Halep broke for a 5-4 lead — after Kenin saved two break-point chances — and calmly closed it out in 2 hours, 31 minutes.
“I have no idea how I won tonight,” Halep said. “So hard to explain what happened on court.”