Replay is a fantasy novel by American writer Ken Grimwood, first published by Arbor House in 1986. It won the 1988 World Fantasy Award for Best Novel.
The novel tells of a 43-year-old man who dies and wakes up back in 1963 in his 18-year-old body. He relives his life with all his memories of the previous 25 years intact. This happens repeatedly, with the man playing out his life differently in each cycle. The novel was a bestseller in Japan. Its time-loop concept has been referenced as a precursor of Harold Ramis' comedy-drama Groundhog Day (1993). Richard A. Lupoff explored a similar premise in his 1973 short story "12:01".
Ken Grimwood was working on a sequel to Replay when he died from a heart attack in 2003 at the age of 59 RIP. In 2010 Warner Bros. reported that it was planning on a film version starring Ben Affleck. The screenplay for this adaptation has been written by Jason Smilovic. In 2011, Robert Zemeckis was in talks to direct.