Dr. Philip Nitschke (pronounced /ˈnɪtʃki/) (born 8 August 1947) is an Australian medical doctor, humanist and founder and director of the pro-euthanasia group Exit International. He successfully campaigned to have a legal euthanasia law passed in Australia's Northern Territory and assisted four people in ending their lives before the law was overturned by the Federal government. Nitschke was the first doctor in the world to administer a legal, voluntary, lethal injection.

Born in 1947 in rural South Australia, Nitschke studied physics at the University of Adelaide, gaining a PhD from Flinders University in laser physics in 1972. Rejecting a career in the sciences, he instead travelled to the Northern Territory to take up work with the Aboriginal land rights activist, Vincent Lingiari and the Gurindji at Wave Hill.

After the hand-back of land by then Prime Minister Gough Whitlam, Nitschke became a Northern Territory Parks and Wildlife ranger. However, a serious accident to his foot saw him return to university, graduating from Sydney University Medical School in 1988.