Theresa Penelope Irwin (née Raines), AM (born July 20, 1964) is an American-born naturalist, author, the widow of Australian naturalist Steve Irwin, and owner of Australia Zoo at Beerwah, Queensland, Australia. She co-starred with her husband on The Crocodile Hunter, their unconventional television nature documentary series, as well as their spin-off series, The Crocodile Hunter Diaries and the Croc Files. She has lived in Australia since 1992, when she married Steve Irwin.

Terri was born in Eugene, Oregon in the United States of America, the youngest of three daughters. Her family was in the trucking business. As a small child, her father constantly brought home injured animals from the highways on which his trucks travelled; this eventually instilled in her an ongoing commitment to saving and rehabilitating wild animals.

While working in the family business in 1986, Terri started a rehabilitation facility called "Cougar Country" to re-educate and release predatory mammals such as foxes, opossums, raccoons, bears, bobcats, and cougars back into the wild. Soon she was handling 300 animals each year.