Robert Irwin was born on 1 December 2003, the second of two children and only son of late Australian television personality and environmentalist Steve Irwin and of Terri Irwin and the grandson of the naturalist and animal conservationist Robert "Bob" Irwin. He is of English and Irish ancestry, with abundance of Irish ancestry on his father's side. Both Robert and his sister Bindi Irwin were homeschooled at Australia Zoo.
During a public show on 2 January 2004 when Irwin's father Steve carried Robert, then one month old, in his arm while hand-feeding a chicken carcass to a 3.8-metre (12 ft 6 in) saltwater crocodile. Robert Irwin was close to the crocodile, and comparisons were made in the press to Michael Jackson's dangling his son outside a German hotel window. The incident prompted the Queensland government to change its crocodile-handling laws, banning children and untrained adults from entering crocodile enclosures.
When Robert was almost three years old, Steve died from his injuries and blood loss in a stingray attack.
In 2009, Irwin had a cameo appearance in Free Willy: Escape from Pirate's Cove. In 2012, Irwin appeared alongside his mother and sister in a TV series entitled Steve Irwin's Wildlife Warriors, which earned him a 2013 Logie Award nomination for Most Popular New Male Talent. In 2014 and 2015, Irwin co-hosted a TV series named Wild But True on Discovery Kids Channel. The show was later nominated for an International Emmy Kids Award in the factual category in 2016.