Dermot Mulroney (born October 31, 1963) is an American actor, musician, and voice actor. He is best known for his roles in romantic comedy, western, and drama films. Appearing on screen since the mid-1980s, he is known for his work in films such as Young Guns (1988), Staying Together (1989), Where the Day Takes You (1992), Point of No Return (1993), Angels in the Outfield (1994), My Best Friend's Wedding (1997), About Schmidt (2002), The Wedding Date (2005), August: Osage County (2013), Insidious: Chapter 3 (2015), and the HBO films The Last Outlaw (1993) and Long Gone (1987). Mulroney played the main antagonist Francis Gibson in NBC's Crisis, Dr. Walter Wallace in Pure Genius, Sean Pierce in Showtime's Shameless and Bobby Sheridan in USA's The Purge.
Mulroney was born in Alexandria, Virginia. His father Michael Mulroney, originally from Elkader, Iowa, was a law professor at Villanova University School of Law beginning in the 1990s, prior to which he had a private practice in tax law for thirty years in Washington, D.C. His mother, Ellen, originally from Manchester, Iowa, was a regional theater actress. Dermot is the middle child among five siblings. He has two older brothers, Conor and Sean; a younger brother, Kieran Mulroney, who is an actor and screenwriter; and a younger sister, Moira. Mulroney attended Matthew Maury Elementary School and played cello in school and city youth orchestras, as well as acted in children's community theater. He finished 9th and 10th grades at George Washington High School, before attending T. C. Williams High School (class of 1981) in Alexandria, Virginia. During his sophomore year in high school, he attended the Interlochen Arts Camp as a cellist. Beginning at age 18, Mulroney studied communications at Northwestern University in Evanston, Illinois, where he was a member of the Phi Gamma Delta fraternity, and graduated in 1985.