Rebecca Augusta Miller, Lady Day-Lewis (born September 15, 1962) is an American filmmaker and novelist. She is known for her films Angela (1995), Personal Velocity: Three Portraits (2002), The Ballad of Jack and Rose (2005), The Private Lives of Pippa Lee (2009), and Maggie's Plan (2015), all of which she wrote and directed, as well as her novels The Private Lives of Pippa Lee and Jacob's Folly. Miller received the Sundance Film Festival Grand Jury Prize for Personal Velocity and the Gotham Independent Film Award for Breakthrough Director for Angela.

Miller is the daughter of Arthur Miller, a Pulitzer Prize-winning playwright, and his third wife, Inge Morath, a Magnum photographer.