The Olympic marathon Swim Qualifier will be held in Setubal, Portugal over a distance of 10km. The same city hosted the Olympic Games Qualifying event both in 2012 and 2016.
A total of fifteen place are at stake for both 10km event (men and women)
The nine highest placed athletes for each event will obtain one quota place. Only NOCs/NFs that have no athlete qualified through the FINA World Championships 2019 may elect to send a maximum of two athletes per event. Each NOC/NF can qualify a maximum of one (1) athlete per gender.
In regards to the continental representation, the highest placed athlete in the 10km event, not yet qualified, from each of five (5) Continents will directly qualify.
Should an NOC/NF have previously qualified one (1) or two (2) athletes, the next highest ranked athlete from the same continent, not yet qualified, in the ranking of the FINA Olympic Marathon Swim Qualifier 2021 event will qualify to ensure that each of these competitions yields a competitor.
The Host Country will automatically qualify one quota for men and one for women.