Venus Williams returns to the year-end WTA Finals for the first time since 2009 and will face Karolina Pliskova on Sunday.
The top eight players in the world will play in the round-robin event, which also features No. 1 Simona Halep, Garbine Muguruza, Elina Svitolina, Caroline Wozniacki, Jelena Ostapenko and Caroline Garcia.
"They're all pretty special," said Williams of her five career appearances in the year-end competition. "Only top eight get here. It's definitely something well-earned."
The 37-year-old Williams is the third-oldest player to qualify for the finals. Billie Jean King was 39 in 1983 and Martina Navratilova was 38 in 1994.