William Patrick Muldoon III was born and raised in the picturesque Los Angeles waterfront town of San Pedro, California, the son of Deanna and William Patrick Muldoon II, a personal injury and maritime attorney with a rich artistic heritage. His parents' creative backgrounds, encompassing painting, writing, music, and athletics, instilled in their son a deep appreciation for the arts and sports. Muldoon's early life was marked by a strong athletic streak, as he played college football for the renowned University of Southern California (U.S.C.) Trojans, earning two Rose Bowl rings.
Following his football career, Muldoon began his journey in the entertainment industry as a model for Calvin Klein and was subsequently signed to the esteemed Wilhelmina Modeling agency. His early television appearances included roles on popular shows such as "Who's the Boss?" (1984) with Tony Danza and "Silk Stalkings" (1991) with Rob Estes, which ultimately led to his breakout role as Austin Reed on the long-running soap opera "Days of Our Lives" (1965). For his outstanding performance, Muldoon won the Soap Opera Digest award for Best New Actor and went on to spend three years at NBC.
As one of the most recognizable faces from the soap opera world, Muldoon caught the attention of Spelling Entertainment, which led to a development deal and a subsequent season on the hit television series "Melrose Place" (1992). His next major breakthrough came when he landed the role of Zander Barkalow in Paul Verhoeven's science fiction epic "Starship Troopers" (1997) alongside Casper Van Dien.
Muldoon has since appeared in a diverse range of independent films, including the Sundance contestant "Wicked" (1998) with Julia Stiles and Frank Darabont's "Black Cat Run" (1998). In 2011, he returned to "Days of Our Lives" (1965) for a year, before starring in a string of television movies and films, including "All About Christmas Eve" (2012) with Haylie Duff for Lifetime, "_Holiday Road Trip_" with Ashley Scott and George Hamilton, and "In the Dark" (2013) with Elisabeth Röhm for Lifetime.
In addition to his acting career, Muldoon has also ventured into music, releasing an EP titled "Muldoon and Ives" in 2019, which is available on all major streaming platforms. He is also a skilled martial artist, holding a blue belt in Krav Maga and frequently incorporates his training into his fight scenes.