Justin Paul Theroux (/θəˈroʊ/; born August 10, 1971) is an American actor and filmmaker. He gained recognition for his work with director David Lynch in the mystery film Mulholland Drive (2001) and the horror film Inland Empire (2006). He also appeared in films such as Romy and Michele's High School Reunion (1997), American Psycho (2000), Charlie's Angels: Full Throttle (2003), Strangers with Candy (2005), Miami Vice (2006), Wanderlust (2012), The Girl on the Train (2016), The Spy Who Dumped Me (2018), On the Basis of Sex (2018), Bumblebee (2018), Lady and the Tramp (2019), and Beetlejuice Beetlejuice (2024).

Theroux was a screenwriter for films such as the action comedy Tropic Thunder (2008), the superhero film Iron Man 2 (2010), and the musical comedy drama Rock of Ages (2012). He made his directorial debut with the romantic comedy film Dedication (2007).