The MY Steve Irwin is a 59-metre (194 ft) motor vessel that previously was the flagship of the Sea Shepherd Conservation Society, and was used in their direct action campaigns against whaling and against illegal fisheries activities.

The vessel was built in 1975 and formerly served as a Scottish Fisheries Protection Agency conservation enforcement patrol boat, the FPV Westra, for 28 years.

In February 2007, Robert Hunter joined Farley Mowat in order to prevent the Japanese whaling vessel Nisshin Maru from hunting in an action Sea Shepherd called Operation Leviathan.

On January 15, 2008, after throwing packages of butyric acid onto the decks and attempting to entangle a hunting ship's propeller,[11] two Sea Shepherd members boarded the Japanese whaling vessel Yūshin Maru No.

[13] Benjamin Potts, a 28-year-old cook from Sydney, Australia, and Giles Lane, a 35-year-old engineer from Leeds, United Kingdom, were detained by crew of Yūshin Maru No.

In a letter faxed to Steve Irwin, the ICR stated that part of the handover conditions include that Sea Shepherd "must not take any violent action or video/photo shooting activities against us.

[23] Conversely, Steve Irwin 1st Officer Peter Brown stated that "the Institute of Cetacean Research is acting like a terrorist organisation [...] Here they are taking hostages and making demands.

[27] The Japanese-based Institute of Cetacean Research claimed that MY Steve Irwin deliberately turned into the stern side of the vessel Yūshin Maru No.

[30] After three days, a suspected Japanese-chartered aircraft located the Steve Irwin en route to the Southern Ocean and instructed the MV Shōnan Maru 2 to observe the movements of the vessel.

Ultimately, Steve Irwin returned to Australia, where Shōnan Maru was unable to track her due to a heavy storm, in addition to legal complications.

After the loss of MY Ady Gil in a collision with Shonan Maru No.2, Steve Irwin met up with MY Bob Barker, with which she exchanged fuel, supplies, and crew.

Once the two Sea Shepherd vessels had linked up, Steve Irwin took up position behind Nisshin Maru to obstruct the factory ships slipway and engaged her with water cannon.

[45] On January 5 Steve Irwin arrived in Fremantle Harbour escorting the severely damaged Brigitte Bardot from the Southern Ocean, monitored by the Japanese whaling ship Shōnan Maru 2.

[50] While Japan agreed to release the activists, the Australian Prime Minister Julia Gillard slammed the action as "unacceptable" and warned that others who carry out similar protests would be "charged and convicted".

[51] On February 20, Sea Shepherd Conservation Society founder Paul Watson claimed the Japanese whaling ship Nisshin Maru rammed Steve Irwin, MY Sam Simon and Bob Barker multiple times in a confrontation in the Southern Ocean, north of Australia's Casey Research Station in Antarctica.

[52] On December 2, 2018 Sea Shepherd announced that the ship will be retired, stripped and recycled in China, and the MY Ocean Warrior will be taking its spot as the flagship vessel of the fleet.

Currently there is a basic Sea Shepherd Museum, bar, cafe, ship tours, weekend and monthly events [55] The vessel is temporarily in Newcastle Harbour for repairs and plans to eventually head north to Brisbane.