Melbourne - Dominic Thiem edged closer to his mum getting a kangaroo tattoo after the world No 5 swatted aside an error-prone and underarm-serving Gael Monfils to book a maiden Australian Open quarter-final on Monday.

The two-time Roland Garros finalist proved too wily for his experienced French opponent, crushing him 6-2, 6-4, 6-4 on Rod Laver Arena.

It set up a last-eight showdown with either world number one Rafael Nadal or temperamental Australian Nick Kyrgios, who play later.

Thiem revealed that he made a pact with his mother Karin last year that each time he won a title she would get a tattoo to mark the occasion.

"After a pretty bad start to the season last year after some losses she said after a long trip to Indian Wells from Rio, all really jet-lagged, that if I won that she would get a tattoo," the Austrian said.

"I ended up winning that one so this tradition started."

She has since got tattoos of an eagle feather to mark winning in the United States and a panda after he claimed a title in China.

Asked what she would be marked with if he clinches the Australian Open, he replied: "For sure a kangaroo."

Thiem has long had the measure of Monfils, winning all five of their previous encounters, and the 10th seed had no answers on a hot Melbourne day, making 32 unforced errors.

"I played my best match so far, I had a good feeling," said Thiem, the first player from Austria to reach the last eight at Melbourne Park since Stefan Koubek in 2002.

"But the score looks much easier than the match was. I always play my best tennis against Gael."

Monfils is a nine-time Grand Slam quarter-finalist but only one of them came in Melbourne and he never looked like reaching a second.

The Austrian, targeting a maiden Grand Slam crown, went a break up for 2-1 in the opening set and then grabbed another as Monfils struggled to deal with Thiem's accurate and varied first serve.

With Thiem pressing hard again in the second set, Monfils tried an underarm serve at 40-30 in game three. It worked, catching the Austrian off-guard.

But it only delayed the inevitable. With Monfils appearing to struggle in the heat, Thiem created four break points in game seven and the Frenchman finally succumbed by missing an easy net volley.

The third set followed a similar pattern with Thiem breaking early and quickly completing a routine victory.