Born to Lyn and Bob Irwin in Essendon, a suburb of Melbourne, Victoria, Irwin moved with his parents as a child to Queensland in 1972. Bob was a reptile enthusiast and when the family moved, Bob and Lyn Irwin started the small Queensland Reptile and Fauna Park, where Steve grew up around crocodiles and other reptiles.

Irwin became involved with the park in a number of ways, including taking part in daily animal feedings, as well as care and maintenance activities. On his sixth birthday he was given a scrub python. He began handling crocodiles at the age of nine, after his father had educated him on reptiles from an early age.He graduated from Caloundra State High School in 1979. He soon moved to Northern Queensland became a crocodile trapper, removing crocodiles from near populated areas where they were considered a danger. He performed the service for free with the quid pro quo that he kept them for the park. Crocodiles that he caught were sent down to the family zoo. He stayed in North Queensland for around five years. Irwin followed in his father's footsteps, becoming a volunteer for the Queensland Government's East Coast Crocodile Management program.

The park was a family run business until it was turned over to Irwin in 1991. He took over the running of the park, now called Australia Zoo (renaming it in 1992). Also tyhat year he appeared in a one-off reptile and wildlife special for television. In 1992 he met (at the park, whilst performing a demonstration) and married Terri Raines. The footage, shot by John Stainton, of their crocodile-trapping honeymoon became the first episode of The Crocodile Hunter. The series debuted on Australian screens in 1996, and by the following year had made its way onto North American television. The Crocodile Hunter became wildly successful in the United States and the UK. By 1999 he had become very popular in the United States, making his first appearence on The Tonight Show with Jay Leno. By this time the series was now in broadcast in over 130 countries. His exuberant and enthusiastic presenting style, broad Australian accent, constant wearing of khakis and catch-phrase "Crikey!" became known worldwide.

Under Irwin's expansive leadership, the operations grew to include the zoo, the television series, the Steve Irwin Conservation Foundation, and International Crocodile Rescue. Improvements to the Australia Zoo include the Animal Planet Crocoseum, the rainforest aviary, and Tiger Temple. Irwin mentioned that he was considering opening an Australia Zoo in Las Vegas and possibly other sites around the world.

In 2001, Irwin appeared in a cameo role in the Eddie Murphy film Dr. Dolittle 2. In 2002, his first and only feature film The Crocodile Hunter: Collision Course was released. In general, reviews of this film were negative. Irwin portrayed himself, in addition to performing numerous stunts for the film. The film follows Irwin who mistakes some CIA agents for poachers. He sets out to stop them from capturing a crocodile, who, unknown to him, has actually swallowed a tracking drone. The film won the Best Family Feature Film award for a comedy film at the Young Artist Awards. The film was produced on a budget of about $12 million, and has grossed over $28 million (as of September 2006).In 2003 Irwin was reportedly in line to host a chat show on Australian network television, a series that never went into production.

Animal Planet ended The Crocodile Hunter with a series finale entitled "Steve's Last Adventure." The last Crocodile Hunter documentary went for three hours with footage of Irwin's across-the-world adventure, visiting locations like the Himalayas, the Yangtze River, Borneo, and the Kruger National Park. Irwin went on to star in other Animal Planet documentaries, including The Croc Files, The Crocodile Hunter Diaries, and New Breed Vets.

Irwin feeding a crocodile at Australia Zoo.In January 2006 as part of Australia Week celebrations in the USA, Irwin appeared at the Pauley Pavilion, UCLA in Los Angeles, California. During an interview on The Tonight Show with Jay Leno, Irwin announced that Discovery Kids would be developing a show for his daughter, Bindi Sue Irwin.The show, Jungle Girl, was tipped to be similar to The Wiggles movies, with songs that surround a story. A feature-length episode of Australian kids TV show The Wiggles entitled "Wiggly Safari" appears dedicated to Irwin, and he's featured in it heavily with his wife and daughter. The show includes the song "Crocodile Hunter, Big Steve Irwin".

In 2006, the American network The Travel Channel had begun to show a series of specials starring Irwin and his family as they traveled on cross-country tours.

After questions arose about being paid $175,000 worth of taxpayers' money to appear in a television advertisement and possible political ties, Irwin told the ABC "I love John Howard, and that's the way I am. So everyone thinks I'm, like, this diehard Liberal supporter. I'm not! I'm not. I'm sitting on the fence, mate, I'm a conservationist. I can't afford to be one way or the other. I just have to run straight up the middle, mate. I have to get on with whoever's in power. And to tell you the truth, the best speech that popped up in Parliament House when George Bush was here was Simon Crean. Here's a bloke who actually disagreed with Iraq, OK, so he put forward the most eloquent speech, which really boosted his profile in my eyes. By crikey, I thought, Simon did the best one there, which is fantastic. So I appreciate good work when I see it, and that's all it is." His comments describing John Howard as the "greatest leader in the world" earned him great scorn in the media

A poster from Irwin's Quarantine Matters! campaign.Irwin was also involved in several media campaigns. He enthusiastically joined with the Australian Quarantine and Inspection Service to promote Australia's strict quarantine/customs requirements, with advertisements and posters featuring slogans such as, "Quarantine Matters! Don't muck with it". His payments for these advertising campaigns were directed into his wildlife fund.

In 2004 he was appointed ambassador for The Ghan, an Adelaide to Darwin train that began operations in 2004. For some time he was sponsored by Toyota, in keeping with his rugged outback image.

He was also a keen promoter for Australian tourism in general and Queensland tourism in particular. In 2002 the Australia Zoo was voted Queensland's top tourist attraction.His immense popularity in the United States meant he often promoted Australia as a tourist destination there.

In 2001 Irwin was awarded the Centenary Medal for his "service to global conservation and to Australian tourism".In 2004 he was recognised as Tourism Export of the Year.Also in 2004, he was nominated for Australian of the Year, which was won by Steve Waugh. Doubts were cast over his nomination when the "baby Bob" incident occurred in January that year.

Crocodile Hunter's Steve Irwin dies at 44 Shortly after 11:00 a.m. local time (01:00 UTC) on 4 September 2006, Irwin was fatally pierced in the chest by a short-tail stingray barb while snorkelling in Batt Reef, which is part of the Great Barrier Reef, off the coast of Port Douglas in Queensland, Australia. Irwin was in the area filming his own documentary, to be called The Ocean's Deadliest, but weather had stalled filming. Irwin decided to take the opportunity to film some shallow water shots for a segment in the television program his daughter Bindi was hosting, when, according to his friend and colleague John Stainton, he swam too close to one of the animals. "He came on top of the stingray and the stingray's barb went up and into his chest and put a hole into his heart," said Stainton, who was on board Irwin's boat the Croc One.

The events were caught on camera, and the footage was handed to the Queensland Police. After reviewing the footage of the incident and speaking to the cameraman who recorded it, marine documentary filmmaker and former spearfisherman Ben Cropp speculated that the stingray "felt threatened because Steve was alongside and there was the cameraman ahead." In such a case, the stingray responds by automatically flexing the serrated barb on its tail up to a maximum of 25 cm (10 in) of length. Cropp said Irwin had accidentally boxed the animal in. "It stopped and twisted and threw up its tail with the spike, and it caught him in the chest. It's a defensive thing. It's like being stabbed with a dirty dagger." The stinging of Irwin by the bull ray was "a one-in-a-million thing," Cropp told Time magazine. "I have swum with many rays, and I have only had one do that to me." Some reports have claimed that after the incident, Irwin was shown on tape pulling the barb out, before losing consciousness, but this was both confirmed and denied by his colleague John Stainton in different sources. It is thought, in the absence of a coroner's report, a combination of the toxins and the puncture wound from the barb caused Irwin to die of an apparent cardiac arrest or that he died quickly as a result of a punctured aorta.

Crew members aboard his boat called the emergency services in the nearest city of Cairns and administered CPR as they rushed the boat to nearby Lowe Isle to meet a rescue helicopter. Medical staff pronounced Irwin dead when they arrived a short time later. According to Dr. Ed O'Loughlin, who treated Irwin, "it became clear fairly soon that he had non-survivable injuries." "He had a penetrating injury to the left front of his chest. He had lost his pulse and wasn't breathing."

Irwin's body was flown to a morgue in Cairns. His wife was on a walking tour in Cradle Mountain-Lake St Clair National Park in Tasmania at the time, and returned via a private plane from Devonport to the Sunshine Coast with their two children.

This was only the third known Australian fatality from a stingray, and the first since 1945.[38] As of 1996, only seventeen worldwide fatalities had been recorded, and it is believed to be the only fatality from a stingray ever captured on film.