Daniel Michael Blake Day-Lewis (born 29 April 1957) is an English actor with British and Irish citizenship. He is known as one of the most selective actors in the film industry, having starred in only four films since 1997, with as many as five years between roles. He is a method actor, known for his constant devotion to and research of his roles. Often, he will remain completely in character for the duration of the shooting schedule of his films.

His portrayals of Christy Brown in My Left Foot (1989) and Daniel Plainview in There Will Be Blood (2007) won Academy and BAFTA Awards for Best Actor, and Screen Actors Guild as well as Golden Globe Awards for There Will Be Blood. His role as Bill "The Butcher" Cutting in Gangs of New York earned him the BAFTA Award and a Screen Actors Guild Award.

Day-Lewis was born in London, the son of actress Jill Balcon and the Irish born Poet Laureate Cecil Day-Lewis. His mother was of Baltic Jewish descent, the daughter of Sir Michael Balcon, who was the former head of Ealing Studios. Two years after his birth in London, the Day-Lewis family moved to Croom's Hill, Greenwich, where Daniel grew up along with his older sister, Tamasin Day-Lewis, who later became a documentary filmmaker and television chef. Cecil Day-Lewis was already 53 years old at the time of his son's birth, and seemed to take little interest in his children. Following frequent health problems, he died when Day-Lewis was 15, leaving him feeling unsettled about his lack of emotion, and regretting not having been closer to his father.