The International Swimming League (ISL) is an annual professional swimming league, established in 2019. It features a team-based competition format with fast-paced race sessions. In 2019, the regular season started in October and the Final Match was held in December.

Katinka Hosszú is a Hungarian competitive swimmer specialized in individual medley events. She is a three-time Olympic champion and a nine-time long-course world champion. She is owner of a Budapest based swim school and swim club called Iron Swim Budapest, and co-owner and captain of Team Iron, founding member of the International Swimming League.