The 23-year-old, who won her maiden Grand Slam title at the French Open this year, will be making her singles debut in the October 27-November 3 Finals, which offer $14 million in prize money.
"It's been a goal from the very start of the year to qualify for the WTA Finals," Barty, Australia's first women's number one since Evonne Goolagong Cawley in 1976, told the WTA website.
"I'm proud of the work my team and I have put in to get to this point, and I'm honoured to be among the top eight players of the season."
Serena has 'excellent' chance of French Open glory - Wilander, plus Evert reaction
04/06/2021 AT 16:37
Barty will be the first Australian to compete at the season-ending tournament since Samantha Stosur in 2012.
The top eight singles players will face off in a round-robin format with the winner taking home the Billie Jean King Trophy.
'Dangerous' Serena battles through tough test from Collins in Paris
04/06/2021 AT 14:18
‘It’s heartbreaking’ - Barty after injury forces top seed out of French Open
03/06/2021 AT 12:44