Timothy Blake Nelson (born May 11, 1964) is an American actor and playwright. Described as a "modern character actor, his roles include Delmar O'Donnell in O Brother, Where Art Thou? (2000), Gideon in Minority Report (2002), Doctor Steve Pendanski in Holes (2003), Doctor Jonathan Jacobo in Scooby-Doo 2: Monsters Unleashed (2004), Danny Dalton Jr. in Syriana (2005), Samuel Sterns in the Marvel Cinematic Universe, Richard Schell in Lincoln (2012), the titular character of The Ballad of Buster Scruggs (2018), and Henry McCarty in Old Henry (2021). He portrayed Wade Tillman / Looking Glass in the HBO limited series Watchmen (2019), for which he received a Critics' Choice Television Awards nomination for Best Supporting Actor in a Drama Series in 2020.

Nelson's directorial credits include Eye of God (1997), which was nominated for the Sundance Grand Jury Prize and an Independent Spirit Award; O (2001), a modern-day adaptation of Othello; and the Holocaust drama The Grey Zone (2001). Eye of God and The Grey Zone were both adapted from Nelson's own plays. Nelson has also co-directed music videos for Billy Woods and Kenny Segal, including "Babylon by Bus" and "Soft Landing." He also co-directed the music video for Armand Hammer feat. Pink Siifu's "Trauma Mic."