SeaWorld says it is "deeply saddened" after Tilikum, the orca which killed a trainer at its Orlando facility in 2010, died in captivity.
"Tilikum had, and will continue to have, a special place in the hearts of the SeaWorld family, as well as the millions of people all over the world that he inspired,'' SeaWorld president and CEO Joel Manby said.
"My heart goes out to our team who cared for him like family.''
Tilikum became notorious for his role in several deaths, as well as his part in the documentary Blackfish, which highlighted the effects of captivity on marine mammals.
Tilikum was around 36 years old, and born free off Iceland before being captured.
In 1991 he and two female orcas submerged a part-time trainer and held her underwater until she drowned.
In 1999 a dead man was found in his tank after sneaking in overnight. The autopsy concluded that the cause of death was drowning.
And in 2010, Tilikum killed 40-year-old trainer Dawn Brancheau in front of a live audience, grabbing her and pulling her under the water.
He received further international attention after the documentary Blackfish exposed his ill-treatment and aggressive behaviour - including footage of attacks on trainers by Tilikum and other captive orcas.
The filmmakers argued the stress of captivity caused Tilikum's aggression, and sparked debate on the ethics and consequences of keeping killer whales in captivity.
In 2016 SeaWorld announced it would end its orca breeding program and shows.
It did not give the cause of Tilikum's death.