The 44-year old was filming an underwater documentary on Monday morning, and police sources in Cairns, north Australia, say he was killed by a stingray barb.
Only the second known Australian fatality from a stingray attack, Irwin seemed to have been stung either through his heart or the left side of his chest, following which he immediately suffered a cardiac arrest. He is survived by wife Terri and their two children, Bindi Sue, 8, and Robert, 3.
Also aiding his global following were his pro-conservation, environmentalist approach and his encyclopaedic knowledge and love of crocodiles.
Australian naturalist and animal-lover Steve Irwin has died after being struck in the chest by a stingray's barb.
Irwin had been filming a documentary on his boat Croc One in Queensland's Great Barrier Reef on the day of his death. Paramedics were unable to save his life.
The 44-year-old was famous around the world for handling dangerous animals, including an anaconda during a TV appearance on the Jay Leno Show.
Mr Irwin's wife Terri was often at his side, to help deal with animals such as the albino Burmese python.
Father-of-two Mr Irwin grew up on his parents' reptile park and became fascinated with animals after receiving a python as a present on his sixth birthday.
He was also a passionate conservationist and was pictured with a variety of animals, such as Kimberly the camel in 2003.
There was outrage in 2004 when Mr Irwin held his one-month-old son near a crocodile during a show. He said his children, including daughter Bindi, had to grow up to be "croc savvy".
Mr Irwin, who handled dangerous animals such as the taipan snake, turned a small reptile park in Queensland into Australia Zoo. It has now become a major wildlife centre.
And Mr Irwin emphasised his dedication to saving endangered species by creating the Steve Irwin Conservation Foundation.
Australian Foreign Minister Alexander Downer said he was "fond" of Mr Irwin and "very, very appreciative" of his work in promoting Australia overseas.
Fans left flowers at Australia Zoo after news of Mr Irwin's death was confirmed on Monday.
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