is an American actor. He has played supporting roles in films such as Brokeback Mountain (2005), Awake (2007), Revolutionary Road (2008), State of Play (2009), W.E. (2011), A Walk Among the Tombstones (2014), Black Mass (2015), Suicide Squad (2016), Sleepless (2017), No Sudden Move (2021), and Gran Turismo (2023).

Harbour gained global recognition for his portrayal of Jim Hopper in the Netflix science fiction series Stranger Things (2016–present), for which he received a Critics' Choice Television Award in 2018, two Emmy Award nominations and a Golden Globe Award nomination. He played the title character in Hellboy (2019), Red Guardian in Black Widow (2021), and Santa Claus in Violent Night (2022).