There Will Be Blood is a 2007 American epic period drama film written and directed by Paul Thomas Anderson, loosely based on the 1927 novel Oil! by Upton Sinclair. It stars Daniel Day-Lewis, Paul Dano, Kevin J. O'Connor, Ciarán Hinds, and Dillon Freasier. The film follows silver miner-turned-oilman Daniel Plainview (Day-Lewis) as he embarks on a ruthless quest for wealth during the Californian oil boom between the late 19th and early 20th centuries.

Development on There Will Be Blood began after writer Eric Schlosser purchased the film rights to Sinclair's novel in 2004: it was acquired by Ghoulardi Film Company, Paramount Vantage and Miramax Films after Anderson completed the first draft of the film's screenplay. Day-Lewis immediately joined the project while Dano, who initially signed on for a smaller role, took on a starring role after replacing Kel O'Neill during filming. Principal photography began in June 2006 and lasted until that September, with filming locations including Los Angeles and Marfa, Texas. The film's music was composed by Radiohead guitarist Jonny Greenwood.

There Will Be Blood premiered at Fantastic Fest in Austin on September 29, 2007: it was first theatrically released in New York City and Los Angeles on December 26 and in selected international markets on January 25, 2008. It grossed $76.1 million worldwide and received acclaim from critics, with praise for the cinematography, Anderson's direction, screenplay, music, and performances of Day-Lewis and Dano. The National Board of Review, the American Film Institute and the National Society of Film Critics named There Will Be Blood one of the top-ten films of 2007. The film was nominated for eight awards at the 80th Academy Awards, winning two (Best Actor for Day-Lewis and Best Cinematography) and received numerous other accolades. It has since been widely regarded as one of the greatest films of the 21st century.