Day-Lewis’ spokeswoman, Leslee Dart, confirmed the news: “Daniel Day-Lewis will no longer be working as an actor. He is immensely grateful to all of his collaborators and audiences over the many years. This is a private decision and neither he nor his representatives will make any further comment on this subject."
He's the only actor to ever win three Academy Awards for Best Actor, for his roles in "My Left Foot", "There Will Be Blood", and most recently "Lincoln".
Source: 1, 2