The 2021 International Swimming League was the third edition of the International Swimming League, a professional swimming league, established in 2019. It comprised ten teams composed of both women and men. The league, due to COVID-19 pandemic travel restrictions, consisted of a total of eighteen short course swimming meets, called matches, spanning four stages of competition and held in two locations. In each match, swimmers from four different teams competed in individual, relay, and skins events. The ten regular season matches and one play in match took place in the city of Naples, Italy. The six play off matches in the semifinals stage of competition took place in the city of Eindhoven, Netherlands, as did the final match.
