Betrayal is a play written by Harold Pinter in 1978. The play deals with an affair that entangles a married couple, Emma and Robert, and their close friend Jerry (who is also married). The play is innovative in its particular uses of reverse chronology; the first scene in the play takes place after the lovers' affair has been dissolved. But several of the scenes advance the action by moving forward in time as well.

It was first produced by the National Theatre in London on November 15th, 1978. The original cast featured Penelope Wilton as Emma, Michael Gambon as Jerry, Daniel Massey as Robert, and Artro Morris as the waiter. It was designed by John Bury and directed by Peter Hall. Later, it opened on Broadway on January 5, 1980 with Raul Julia as Jerry, Blythe Danner as Emma, and Roy Scheider as Robert.

Betrayal is regarded as one of Pinter's major plays and it produced quited often all over the world.

Due to a program note about the author accompanying productions of the play, stating that he "has lived Antonia Fraser" for "five years"), the biographical context for the play has been attributed erroneously to Pinter's affair with Lady Antonia Fraser, which occurred from 1975 to 1980, while he was still married to Vivien Merchant. (Pinter married Antonia Fraser in 1980, after the Frasers' divorce (1977) and the Pinters' divorce (1980) became final.) In actuality, Pinter explained to his official biographer, Michael Billington, the play is based on an affair he had in 1962-69 with television presenter Joan Bakewell, who was married to producer and director Michael Bakewell at that time.

There has been a 1983 film version of the play starring Jeremy Irons and Ben Kingsley as well as a 2000 off-Broadway production at the Roundabout Theatre with Juliette Binoche, Liev Schreiber, and John Slattery.

The eighth episode of the ninth season of the television situation comedy Seinfeld is an homage to this play. The episode, entitled "The Betrayal", moves backward in time, featuring a plot structure of reverse chronology, and it includes a character named (Peter) Pinter.

The 2000 motion picture Memento also uses reverse chronology featuring multiple flashbacks. This point is discussed by the director, Christopher Nolan, in the supplementary materials available on the DVD.

Harold Pinter plays | 1978 plays