Julian Dana William McMahon is an Australian-American actor and former model. He is the only son of Sir Billy McMahon, a former Prime Minister of Australia. He is best known for his roles as Detective John Grant in Profiler, Cole Turner in Charmed, Christian Troy in Nip/Tuck, Doctor Doom in the Fantastic Four duology, Jonah in Runaways, and Jess LaCroix in CBS crime drama FBI: Most Wanted.

Sir William McMahon was an Australian politician who served as the 20th prime minister of Australia from 1971 to 1972. He held office as the leader of the Liberal Party of Australia. He was a government minister for over 21 years, the longest continuous service in Australian history.