Dermot Patrick Mulroney (born October 31, 1963) is an American actor and musician. He is known for his roles in romantic comedy, western, and drama films.

Mulroney is known for his work in various films such as Long Gone (1987), Young Guns (1988), Staying Together (1989), Where the Day Takes You (1992), Point of No Return (1993), The Last Outlaw (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), Scream VI, and Anyone but You (2023).

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).