Swimmers and divers from Russia and Belarus can return to international competition as neutrals, says World Aquatics.
The sport’s governing body had banned competitors from both nations following Russia’s invasion of Ukraine in February 2022.
Athletes will only be allowed to take part in individual events and must show they do not support the war.
They will also have to meet other specific criteria to compete.
World Aquatics president Husain Al-Musallam said: “Despite the challenges we face on the international stage, we acknowledge our responsibility to foster a competitive, fair, and inclusive environment for every competitor.”
Those who apply to return under a neutral banner will be ineligible for swimming relays, synchronised diving events, all water polo competitions and artistic swimming events.
No more than one athlete per event from Russia and one from Belarus will also be able to participate at a World Aquatics competition, such as a World Cup or World Championships.
Other measures include being subject to robust anti-doping measures, with neutral athletes also required to wear uniforms that are plain white in colour.
Any distinctive national signs for either Russia or Belarus will also be banned at all World Aquatics competitions.
In March, the International Olympic Committee recommended to sporting federations that Russian and Belarusian athletes should be allowed to compete under a neutral flag but the IOC is yet to make a final decision on whether athletes from the two countries will be able to take part in next year’s Paris Olympics.
World Aquatics will host three World Cup events in October in Berlin, Athens and Budapest with the next World Championships, which is an Olympic qualifying event, to be held in Doha, Qatar in February.