Serena Williams showed unbelievable sportsmanship as she praised and consoled a tearful Dayana Yastremska, who was no match for the 23-time grand slam champion at the Australian Open.

It was a battle of the ages, with 37-year-old Williams facing 18-year-old Yastremska in the third round at Melbourne Park on Saturday.

And Ukrainian teenager Yastremska was outclassed by Williams, who sailed into the last 16 via a 6-2 6-1 victory on Rod Laver Arena.

Yastremska - the first player born in the 2000s to break into the WTA's top 100 last season - was overcome with emotion afterwards, prompting a touching moment between her and Williams.

"You did amazing. You did so well," Williams could be heard saying as she consoled Yastremska.

"You did amazing. Don't cry, you did really well."

Williams, who could face top seed Simona Halep or sister Venus in the round of 16, continued to praise Yastremska in her on-court interview.

"I thought she played amazing, came out swinging. I felt like she came out ready to go," the former world number one added.

"When I was younger I played against Lindsay Davenport, Martina Hingis, Monica Seles. Everyone I faced was in the 'hall of fame'. Every match was intimidating, but you go out and do the best you can.

"How could I forget Venus? She still intimidates me."