Although the official cause of death will not be announced until the completion of a necropsy, veterinarians at the Orlando, Florida marine theme park had said the approximately 36-year-old whale had been fighting a bacterial lung infection since March.
"Tilikum passed away early this morning, January 6, surrounded by the trainers, care staff and veterinarians that provided him around-the-clock world-class care," SeaWorld said on its website.
"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 Joel Manby said in a statement.
The orca had spent 25 years at SeaWorld, where he and others drew huge crowds for their water shows.
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But the company faced criticism from animal rights groups over its treatment of orcas, which opponents say were kept in tanks that are too small, fed improper diets and forced to perform tricks.
SeaWorld came under widespread criticism for its treatment of killer whales after the release of "Blackfish.
The company said in March that it would stop breeding killer whales, and will no longer keep any of the giant sea creatures in captivity after its current generation dies.