The 29-year-old Czech, who won the title on her debut in 2011, will join Ash Barty, Karolina Pliskova, Simona Halep, Bianca Andreescu and Naomi Osaka at the October 27 - November 3 tournament, which offers $14 million (£11.4 million) in prize money.
"I'm so happy to qualify," Kvitova, who won titles in Sydney and Stuttgart and finished runner-up at the Australian Open this year, said in a statement.
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"After a great start to the year in Australia I'm really proud to have secured my spot for the seventh time.
"This will be the third city I have visited for the WTA Finals so I'm excited to see what's in store in Shenzhen."
The top eight singles players face off in a round-robin format at the WTA Finals, with the winner taking home the Billie Jean King Trophy.
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