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).

In animation, Brown has voiced Lex Luthor in the DC Animated Universe (1996–2006) and Mr. Krabs on SpongeBob SquarePants (1999–present). His other animated roles include Long Feng in Avatar: The Last Airbender (2006) and Savage Opress in Star Wars: The Clone Wars (2011–2013). He has also voiced video game characters such as Doctor Neo Cortex and Uka Uka in the Crash Bandicoot franchise (1997–2003) and Hank Anderson in Detroit: Become Human (2018).

Clarence J. Brown III was born on January 5, 1959, in Urbana, Ohio, and had an older sister, Beth, who died in 1964. Their mother, Joyce Helen (née Eldridge), was a conductor, composer and concert pianist. The siblings' father, Clarence J. "Bud" Brown Jr., was a newspaper publisher who helped manage the Brown Publishing Company, the family-owned newspaper business started by Clancy's grandfather, Congressman Clarence J. Brown. From 1965 to 1983, Bud Brown also served as a congressman, in the same seat as his own father, and later as Chairman of the Board of Brown Publishing. The family continued to operate the business until 2010.

Brown graduated from St. Albans School in Washington, D.C., and Northwestern University. At St. Albans, Brown performed the role of Deputy Governor Thomas Danforth in The Crucible.