Sir Daniel Michael Blake Day-Lewis (born 29 April 1957) is an English retired actor. Often described as one of the preeminent actors of his generation, he received numerous accolades throughout his career which spanned over four decades, including three Academy Awards for Best Actor, making him the first and only actor to have three wins in that category, and the third male actor to win three competitive Academy Awards for acting, the sixth performer overall. Additionally, he has received four British Academy Film Awards, three Screen Actors Guild Awards and two Golden Globe Awards. In 2014, Day-Lewis received a knighthood for services to drama.

Born and raised in London, Day-Lewis excelled on stage at the National Youth Theatre before being accepted at the Bristol Old Vic Theatre School, which he attended for three years. Despite his traditional training at the Bristol Old Vic, he is considered a method actor, known for his constant devotion to and research of his roles. Displaying a "mercurial intensity", he would often remain completely in character throughout the shooting schedules of his films, even to the point of adversely affecting his health. He is one of the most selective actors in the film industry, having starred in only six films since 1998, with as many as five years between roles. Protective of his private life, he rarely grants interviews, and makes very few public appearances.

Day-Lewis shifted between theatre and film for most of the early 1980s, joining the Royal Shakespeare Company and playing Romeo Montague in Romeo and Juliet and Flute in A Midsummer Night's Dream. Playing the title role in Hamlet at the National Theatre in London in 1989, he left the stage midway through a performance after breaking down during a scene where the ghost of Hamlet's father appears before him—this was his last appearance on the stage. In 1984, he appeared in The Bounty before gaining critical attention for his performances in Stephen Frears' My Beautiful Laundrette (1985) and James Ivory's A Room with a View (1986). He then assumed leading man status in Philip Kaufman's The Unbearable Lightness of Being (1988) and My Left Foot (1989), receiving his first Academy Award and British Academy Film Award for Best Actor for his performance in the latter film. He then starred in Michael Mann's historical war film The Last of the Mohicans (1992), Jim Sheridan's courtroom drama In the Name of the Father (1993) and Martin Scorsese's period romance The Age of Innocence (1993).

Following his performance in The Boxer (1997), Day-Lewis retired from acting for three years, taking up a new profession as an apprentice shoe-maker in Italy. He returned to acting in 2000, reuniting with Scorsese in the historical crime film Gangs of New York (2002), winning a British Academy Film Award and receiving an Academy Award nomination. He won the Academy Award and British Academy Film Award for Best Actor for Paul Thomas Anderson's period drama There Will Be Blood (2007) and Steven Spielberg's biographical drama Lincoln (2012). After a decade, Day-Lewis reunited with Anderson for Phantom Thread (2017), for which he was also nominated for an Academy Award. He then announced his retirement following the completion of the film.