Steve Irwin, the ebullient Australian TV personality and conservationist known as the Crocodile Hunter, was killed today by a stingray barb to the heart during a diving expedition.
Irwin, 44, was filming an underwater sequence for a television series on remote Batt Reef off the far north-east coast of Australia when he encountered the ray and was stung at about 11am (0200BST), accoring to a statement from Australia Zoo, Irwin's park.
Crew members aboard Irwin's boat, Croc One, called emergency services in the nearest city, Cairns, and administered attempted resuscitation as they rushed the boat to nearby Low Isle to meet a rescue helicopter.
Medical staff pronounced Irwin dead at about noon, the statement said.
"The world has lost a great wildlife icon, a passionate conservationist and one of the proudest dads on the planet," said John Stainton, Irwin's friend and producer who was on board Croc One.
"He died doing what he loves best and left this world in a happy and peaceful state of mind," he said. "Crocs Rule!"
Queensland state police said Irwin's family - which includes US-born wife Terri - had been notified of his death.
Irwin is famous for his enthusiasm for wildlife and his catchphrase "Crikey!" in his television programme, Crocodile Hunter, which was first broadcast in Australia in 1992 before it was picked up by the Discovery channel, catapulting him to international celebrity.
Irwin, who made a trademark of hovering dangerously close to untethered crocodiles, often leaping on their backs, talked mile-a-minute in a thick Australian drawl and was almost never seen without his uniform of khaki shorts and shirt and heavy boots.
His ebullience was infectious and Australian officials sought him out for photo opportunities and to promote Australia internationally. Irwin was among guests hand-picked by Prime Minister John Howard to attend a barbecue to honour US President George Bush when he visited Canberra, the national capital, in 2003.
The public image was dented in 2004 when Irwin triggered an uproar by holding his baby in one arm while feeding large crocodiles inside a zoo pen. Irwin claimed at the time there was no danger to his son, and authorities declined to charge Irwin with violating safety regulations.
Later that year, he was accused of getting too close to penguins, a seal and humpback whales in Antarctica while making a documentary. Irwin denied any wrongdoing, and an Australian Environment Department investigation recommended no action be taken against him.
He is survived by his wife, from Oregon, who was Terri Raines before they married in 1992, their daughter Bindi Sue, eight, and son Bob, who will turn three in December.
Foreign Minister Alexander Downer, who used a photograph of his family at Australia Zoo for his official Christmas card last year, hailed Irwin for his work in promoting Australia through projects such as the "G'Day LA" tourism and trade promotion in Los Angeles in January.
"The minister knew him, was fond of him and was very, very appreciative of all the work he'd done to promote Australia overseas," Downer's spokesman Tony Parkinson said.