Each National Olympic Committee can enter a maximum of 56 athletes (28 men and 28 women) with a maximum of two athletes per individual event and one team per relay event. To qualify in a relay event a nation must finish in the top 12 during the heats at the 2019 World Aquatics Championship. Four more spots will go to the highest ranked nations based on their best performance at an approved competition between March 1st 2019 and May 31st 2020.
In total, 878 athletes will qualify through four methods. Athletes which have swam the Olympic Qualifying Time (OQT) in an approved competition in at least one event between March 1st 2019 and June 29th 2020 will qualify, with a maximum of two athletes per event. Should a nation fail to qualify a male and/or female athlete, they will be allowed to enter one man and/or woman as a Universality Place in one event provided that they competed at the 2019 World Aquatics Championship. Nations which have qualified a relay may select relay-only athletes (up to # of relays qualified * 2 athletes) to compete provided that the athletes have reached the Olympic Selection Time (OST). Afterwards, any remaining places will go to athletes which have swam an OST in an approved competition with priority going to the highest ranked athletes on the FINA World Rankings of each event until the quota of 878 has been reached. A nation can only qualify a maximum of one athlete per event through this method and none in events where an athlete from the same nation already qualified through the first method.
In the open water event, each National Olympic Committee can enter a maximum of 4 athletes (2 men and 2 women). As hosts, Japan will be given 2 athletes (1 man and 1 woman) to compete should they fail to qualify normally. The remaining quotas will be decided at the 2019 World Aquatics Championship and 2020 Olympic Marathon Swim Qualifier. Continental quotas will be decided at the 2020 Olympic Marathon Swim Qualifier.
Qualification events are listed in hierarchical order. OQTs and OSTs will be posted after FINA approval in December 2018.