AUCKLAND (AFP) - Serena Williams ended a three-year title drought and donated her winner's cheque to victims of the Australian bush fires in an emotional WTA Auckland Classic final on Sunday.

Williams raised expectations for this month's Australian Open, where she can equal Margaret Court's record of 24 Grand Slam titles, with her 6-3, 6-4 victory - her first WTA trophy since she won in Melbourne in 2017.

But the 38-year-old tempered celebrations as she donated her US$43,000 (S$58,000) prize money to the Australian bush fire relief fund and described how the tragedy had affected her deeply.

"I've been playing in Australia for over 20 years and it's been really hard for me to watch all the news and everything that has been happening in Australia with all the fire and... animals and people that have lost their homes," she said.

"I decided at the beginning of the tournament... I'd donate all my prize money for a great cause."

It is her first title as a mother - since she won the Australian Open while pregnant. Her 73 WTA titles now stretch across four decades, after she won her first in 1999.

The tournament top seed slipped 1-3 behind in the first set against the unseeded Pegula, a fellow American.

But once she found her range there was never any doubt about the final result, which Williams greeted by raising her arms in triumph while her husband Alexis Ohanian and two-year-old daughter Olympia looked on.

"It's been a long time, I think you could see the relief on my face," she said, adding she could feel her game sharpening up as she prepares to head to Melbourne.

"It definitely feels good, it feels like i was definitely improving as the week went on and obviously I needed to."

Williams, whose last tournament was the US Open in September, was looking for as much game time as possible in Auckland and an hour after winning the singles crown she was back on court partnering Caroline Wozniacki in the doubles final.

However, the pair were beaten 6-4, 6-4 by Americans Asia Muhammad and Taylor Townsend.