The Danish world number three was beaten 6-4 6-4 by the 18-year-old Canadian in the last 16 in Auckland.

The top seed, who landed a Grand Slam title at the 43rd attempt last January, was punished for failing to convert her break points by the world number 152.

Andreescu will next face seven-time Grand Slam champion Venus Williams.

"Honestly, I can't believe it right now. I've dreamed of playing on this stage against top players and now I'm here," Andreescu said.

Sixth seed Williams beat fellow American Lauren Davis 6-4 6-3 to reach the quarter-finals. Earlier in the week she had watched Wozniacki play, possibly expecting to be facing her in the last eight.

But the 28-year-old Dane squandered 10 of her 12 break points against Andreescu to make an early exit after an encounter lasting two hours 12 minutes.

Meanwhile, in Brisbane it looked like US Open champion Naomi Osaka would also find her first tournament of the year coming to an end before she fought back to beat Latvia's Anastasija Sevastova 3-6 6-0 6-4.

The 21-year-old Japanese player will face Ukraine's Lesia Tsurenko or Estonian Anett Kontaveit in the semi-finals.

The Australian Open, the first Grand Slam tournament of the year, starts on 14 January.