The female whale shark had been rescued after being found in distress in the Arabian Gulf in 2008. But animal rights activists said the fish, dubbed Sammy, had been kept by the Atlantis as a tourist attraction and campaigned for its release.
The hotel said in a statement its fish husbandry team had worked toward Sammy's release in accordance with international conventions on endangered species and she had been set free in the ocean.
"We will continue to track her progress through a tagging program co-developed with The Mote Marine Laboratory in Florida," said Steve Kaiser, vice president of marine and science engineering at the Atlantis.
Whale sharks are the world's largest fish species and grow to an average of around 8 meters length. They are found all over the world in tropical or warm seas.
Sammy's capture had caused a public outcry in Gulf Arab emirate Dubai. Daily newspaper Gulf News launched a "Free Sammy" campaign and residents set up groups on social networking site Facebook calling for her release.
