Clarence John "Clancy" Brown III (born January 5, 1959) is an American actor. Prolific in film and television since the 1980s, Brown is often cast in villainous and authoritative roles.

His film roles include Rawhide in The Adventures of Buckaroo Banzai Across the 8th Dimension (1984), the Kurgan in Highlander (1986), Sheriff Gus Gilbert in Pet Sematary Two (1992), Capt. Byron Hadley in The Shawshank Redemption (1994), Sgt. Charles Zim in Starship Troopers (1997), Surtur in Thor: Ragnarok (2017), Stanley Thomas in Promising Young Woman (2020), and the Harbinger in John Wick: Chapter 4 (2023). On television, he has played Brother Justin Crowe on the HBO series Carnivàle (2003–2005), Waylon "Jock" Jeffcoat on the Showtime series Billions (2018–2019, 2023), Kurt Caldwell on the Showtime series Dexter: New Blood (2021–2022), and Sal Maroni in The Penguin (2024).