Dermot Mulroney (born October 31, 1963) is an American actor. He is known for his roles in romantic comedy, western, and drama films. Appearing on screen since 1986, he is known for his work in various 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), Zodiac (2007), 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 (2014), Dr. Walter Wallace in Pure Genius (2016–2017), Sean Pierce in Showtime's Shameless (2015–2017) and Bobby Sheridan in USA's The Purge (2018–2019).

Filmography