Australia's Ash Barty has claimed the biggest winner's cheque in tennis history, beating Ukraine's Elina Svitolina 6-4, 6-3 to win the WTA Finals title and a $US4.42 million ($6.4 million) prize packet.

Key points: Barty is the first Australian woman to win the season-ending showpiece tournament since 1976

Barty is the first Australian woman to win the season-ending showpiece tournament since 1976 She is also the first Australian woman since rankings were introduced in 1973 to finish the year as world number one

She is also the first Australian woman since rankings were introduced in 1973 to finish the year as world number one She banked more than $US10 million in winnings in 2019

The cheque could have been even bigger, at $6.8 million, had she gone through the tournament undefeated, but a first-up loss to Kiki Bertens in the round-robin stage cost the world number one a few hundred thousand dollars.

The 23-year-old is the first Australian woman to win the season-ending showpiece tournament since Evonne Goolagong Cawley won the crown for a second time in 1976.

It capped a superb week in Shenzhen for Barty, who, in addition to claiming the fattest winner's cheque in tennis history — for male or female competitors — also became the first Australian woman to end the year as world number one since rankings were introduced in 1973, and pushed her annual prize money beyond $US10 million.

Ash Barty is the first Australian to win the season-ending showpiece tournament in 43 years. ( Reuters: Aly Song )

Perhaps unsurprisingly in a battle between the best servers in the tournament, Barty and Svitolina traded service games through the first set of the decider, until the Australian finally broke in a lengthy 10th game to take the first set 6-4.

Things were back on serve through the first two games of the second set, before a series of errors and a double fault by Barty handed Svitolina a break, but the Aussie put the set back on parity at 2-2 with a break of her own and held her serve to love to lead 3-2.

Loading

The French Open champion appeared to be on a roll as she broke again on the back of Svitolina's first double fault of the match to reach 4-2, but Barty could not hold her serve in the next game and the match was back on serve once again.

It looked like the run of breaks would continue when Barty replied to reach 15-40 in the next game, only for Svitolina to rattle off three straight points to have advantage, but the rollercoaster continued as Barty fought back to take the break before powering through her service game to hold to love and take out the tournament in style.

"It's been the most incredible year for me," Barty said at the trophy presentation.

"Congratulations to Elina and your team, you've had an exceptional year.

"You're one of the toughest competitors on the tour and I know we'll have many, many more battles in the future."

Both players traded service games to start the match, until Barty finally broke to win the first set. ( AP: Andy Wong )

It was Barty's first win against Svitolina after five straight losses in their clashes since 2017.

Barty started that year ranked 271st in the world, a year after returning to tennis from a brief hiatus as a cricketer with the WBBL's Brisbane Heat.

Her first WTA title in February of 2017, in Kuala Lumpur, suggested the Queenslander was ready to make good on the promise shown by her 2011 junior Wimbledon championship, when she was just 15. She reached the Birmingham and Wuhan finals and, despite not making a big splash in any of the majors, it was enough to end the year as the 17th-ranked player on the women's tour — a jump of 254 places from January 1.

Barty effectively consolidated the next year, making an early final in Sydney before going out in the third round of the Australian Open, then losing to Serena Williams in the second round at the French Open. She won the Nottingham title in the lead-up to Wimbledon, but again fell in the third round at SW19.

A strong finish to the year with another title in Zhuhai allowed her to finish on a career high ranking of 15, before her stellar 2019.

This year she won titles in Miami and Birmingham, but her crowning achievement was her breakthrough major at Roland Garros in May and the world number one ranking was waiting a month later.

The final two majors of the year were perhaps slight disappointments, with fourth-round exits failing to elicit the same excitement as her Paris run, but the year-ending China swing saw her reach a semi-final in Wuhan and a final in Beijing before her record-breaking win in Shenzhen.