Julian Dana William McMahon (জুলিয়ান ডানা উইলিয়াম ম্যাকমাহন) was an Australian–American actor. He was the only son of Sir William McMahon, a former Prime Minister of Australia. He was best known for his roles as Ben Lucini in Home and Away, Detective John Grant in Profiler, Cole Turner in Charmed, Dr. Christian Troy in Nip/Tuck, Doctor Doom in the Fantastic Four duology, Jonah in Runaways, and Jess LaCroix in FBI: Most Wanted. For his performance in Nip/Tuck, McMahon was nominated for the Golden Globe for Best Actor in a Television Drama Series.

McMahon was born in Sydney, the son of Sonia (née Hopkins), an heiress, socialite and fashion icon and William McMahon, a prominent Australian politician. His father was a Member of the Australian House of Representatives and a high-ranking minister in the 23-year Liberal Government for many years before Julian's birth; he became the 20th Prime Minister of Australia in March 1971, when Julian was two years old. His mother left their three children in the care of a nanny to be with her husband in Canberra during his Prime Ministership. He had an older sister, Melinda, and a younger sister, Deborah. He was of Irish descent through his father.

In an interview with the Herald Sun in 2018, McMahon discussed his childhood: "My Dad... was born in 1908. That's a very different time to what it was when he was raising me. He must have gone through a strange misunderstanding of how you were parented in 1908 versus how you parent in 1972; it would have been so conflicting. Also how you be a husband in that period of time would have been different."

McMahon made his television acting debut in the short-lived daytime soap opera The Power, The Passion, where he played Kane Edmonds. He joined the cast of Home and Away as soldier Benito "Ben" Lucini in late 1989, with his first episode airing in February 1990. McMahon chose not to renew his contract, which expired in December 1990, and he departed along with Sharyn Hodgson, who played his on-screen wife Carly Lucini.

In the early 1990s, McMahon struggled to obtain a work permit for the United States and as a result he missed out on a few roles. McMahon's big break Hollywood role was on the soap opera Another World when he was cast as Ian Rain in 1993. The first scene he shot in New York for the show had him emerge from a pool in a speedo at the Cory Mansion. He remembered the experience as "pretty magical".

McMahon jokingly noted in an interview with Jimmy Kimmel that his mother "a very scary lady" because she would visit him on the set of his films and critique his performance when he finished a scene.

In 1994, McMahon married singer and actress Dannii Minogue after meeting on the set of Home and Away in 1991. He starred in her music video clip for the single "This Is It", a song that summed up the couple's relationship and hopes for the future. The newlyweds spent a great deal of their marriage apart, due to McMahon pursuing his roles in the U.S. and Minogue following her music career in England. They divorced a year and a half later, with Minogue stating that her negative relationship with McMahon's mother, Sonia, Lady McMahon, had been an issue from the beginning.

In 1999, McMahon married Baywatch star Brooke Burns. The couple had one child together before divorcing in 2001. McMahon married for the third time in 2014 to Kelly Paniagua. McMahon died from cancer on 2 July 2025, at age 56, in Clearwater, Florida.

McMahon resided in the United States from the 1990s until his death, but said his soul was still Australian: "I feel like I'm Australian on the inside and American on the outside or something. I would never want to leave it behind either. I love Australians, Australianisms, I love my part of being Australian. I love where I grew up and how I grew up and, you know, I wouldn't change it for the world."