The iconic Irwin, 44, known for his enthusiastic handling of even the deadliest of wildlife, was killed when a stingray barb punctured his chest during the filming and underwater documentary off the coast of the state of Queensland.
"It is believed that Mr Irwin collapsed after being stung by a stingray at Batt Reef off Port Douglas at about 11:00 am (0100 GMT). He had been filming a documentary," a statement from the Queensland Police Service said.
"After being stung by a stingray his crew called for medical treatment and the Queensland medical helicopter responded, however Mr Irwin had died," the statement added.
Police said Irwin's family had been informed of his death. Irwin was married to US-born Terri Irwin and the couple had two children aged eight and three.
The larger-than-life Irwin's rallying cry of "crikey" when faced with a crocodile, snake or ferocious-looking spider, made him an Australian icon across the world.
His "Crocodile Hunter" show, in which he appeared in his trademark khaki shorts and shirt, was first broadcast in 1992 and has been shown around the world on cable network Discovery.
Stingrays have between one and six sharp and highly toxic barbs on their tails that they use to defend themselves when they feel threatened, wildlife websites showed.
(ps: The Boyd Family is sad to learn of Steve Irwin's passing. Steve has worked with our local Singapore Zoo on numerous occasions and will be missed by both staff and donors. Our deepest condolences to Steve's family and fans the world over.)