Mollie Grace O'Callaghan, is an Australian swimmer. She was the 2023 world champion in the women's 100m and 200m freestyle individual events, and part of the world champion 4 × 100 m and 4 × 200 m Australian women's relay teams together with 4 × 100 m mixed relay team. As of July 2023 she is the world record holder in the women's individual 200m freestyle.