This is the first time for American Gauff to play in the finals. She qualifies for both the singles draw and the doubles draw, which she will be playing with doubles partner Pegula.
The two are the first American pairing to play in the WTA finals since Serena Williams and Venus Williams qualified back in 2009.
Gauff is also the youngest player since Maria Sharapova in 2005 and the youngest American to qualify since Lindsay Davenport in 1994.
French player Garcia has qualified for the finals in the past. She is now bidding to become the first Frenchwoman to win the Finals since Amelie Mauresmo did so in 2005.
It has been an interesting year for Gauff who reached her first Grand Slam singles title this year at the French Open. She has also cracked into the Top 10 of the world rankings for the first time this year. She has also reached two semifinals this season.
She is also ranked No.1 in the doubles rankings, becoming the second youngest player in the history of the WTA to do so.
As for Garcia, this is a return to form. This is her first WTA Finals in five years. She has won three titles this season, including the Western and Southern Open.
In addition to titles, she has also made it to three semifinals.
The WTA Finals is set to feature the Top 8 singles and doubles players of the season. It will be held in a round-robin format. The singles champion will lift the Billie Jean King trophy and the doubles winner will win the Martina Navratilova Trophy.