A Florida aquarium has reached a deal with animal welfare advocates to release Lolita, a 2,268kg killer whale held in captivity for more than half a century.

The Miami Seaquarium said it had reached a "binding agreement" with the nonprofit Friends of Lolita to return the whale, who recently retired from performances, to an ocean habitat in the north Pacific Ocean within two years.

Lolita, a 57-year-old orca captured in 1970 in a cove off Seattle, is also known as Toki, a name that is short for the whale's Native American name of Tokitae, the Miami Herald reported.

The plan to return Lolita to her natural habitat requires federal approval, according to the newspaper.

The process to return Lolita to her "home waters" was years in the making, beginning with the transfer of the aquarium's ownership to The Dolphin Co, Miami-Dade County Mayor Daniella Levine Cava said.

The company later partnered with the nonprofit to provide medical care to the whale.

The Seaquarium's previous owner, SeaWorld Entertainment, phased out killer whale shows in 2016.

Sea World Australia has never held captive killer whales and has no commercial link to SeaWorld in America.

Lolita, once a top attraction at Seaquarium, was retired from shows in March 2022 after management changed hands.