Isiah Whitlock Jr. (born September 13, 1954) is an American actor. He is most famous for his role on the HBO television series, The Wire as corrupt state senator Clay Davis. In 2011, Whitlock played an insurance agent named Ronald Wilkes in the film Cedar Rapids. Wilkes is a self-described fan of The Wire and does an impersonation of character Omar Little. Whitlock has said that the references to the series were written in before he became involved in Cedar Rapids.

He is also notable for appearing in Spike Lee films She Hate Me and 25th Hour as Agent Amos Flood. In all three projects, Whitlock established a catchphrase from his characters' distinct pronunciation of the word "shit" ("sheee-it").

He appeared as Eugine, a supporting role, in the 2003 film Pieces of April. He had a bit part in Goodfellas as a doctor who gives Henry Hill a Valium while attending to his brother. In 2007, he played Ethan Banks in Enchanted.

Whitlock has made appearances on Chappelle's Show and has played various characters on Law & Order and its' spinoff, Law & Order: SVU. He also appears in promotional spots for the Wii video game Punch-Out!! portraying the character Doc Louis.