The tournament, which features the top eight singles players and doubles teams in the world, will return to Mexico after a gap of one year. The 2021 edition took place in Guadalajara.
Australian Open champion Sabalenka will be joined by four-times Grand Slam champion Iga Swiatek (22), whom she leapfrogged to claim the top ranking for the first time after the U.S. Open earlier this month, the WTA announced on Friday.
The Belarusian is enjoying her best season on the WTA Tour with three titles and three more finals, including one at Flushing Meadows. She will look to improve on her runner-up finish at last year's WTA Finals in Fort Worth.
Former Wimbledon champion Elena Rybakina rounded off the initial set of entrants for the tournament as she became the first player from Kazakhstan to qualify in singles.
The WTA Finals run from October 29 to November 5.