Stewart played forward for the University of Connecticut (UConn) Huskies women's basketball team. She led the Huskies to four national championships, was named the Final Four's most outstanding player a record four times, and was a three-time consensus national player of the year. Prior to her first WNBA game, Stewart signed a multi-year endorsement deal with Nike. She was the 2016 WNBA Rookie of the Year, is a two-time All-Star, and was named the WNBA MVP in 2018. Due to injury, she is not playing in the 2019 season, and the WNBA hired her as a league ambassador for the 2019 season.