Best Actor went to Daniel Day-Lewis, who beat out fellow nominees Bradley Cooper, Denzel Washington, Hugh Jackman, and Joaquin Phoenix, for his portrayal of our sixteenth president in Lincoln. He also won this year's Golden Globe and SAG award for the role.
His win makes history, as he is the only actor to have received the Academy Award for Best Actor three times. I think he may also hold the record for the "most lipstick on face while giving an acceptance speech" category. Day-Lewis has wife Rebecca Miller to thank for that.