Betrayal is a play written by Harold Pinter in 1978. Critically regarded as one of the English playwright's major dramatic works, it features his characteristically economical dialogue, characters' hidden emotions and veiled motivations, and their self-absorbed competitive one-upmanship, face-saving, dishonesty, and self-deceptions.

Inspired by Pinter's clandestine extramarital affair with BBC Television presenter Joan Bakewell, which spanned seven years, from 1962 to 1969, the plot of Betrayal integrates different permutations of betrayal relating to a seven-year affair involving a married couple, Emma (Juliette Binoche)  and Robert (John Slattery), and Robert's friend Jerry (Liev Schreiber), who is also married, to a woman named Judith. For five years Jerry and Emma carry on their affair without Robert's knowledge, both cuckolding Robert and betraying Judith, until Emma, without telling Jerry she has done so, admits her infidelity to Robert (in effect, betraying Jerry), although she continues their affair.

Pinter's particular usage of reverse chronology in structuring the plot is innovative: the first scene takes place after the affair has ended; the final scene ends when the affair begins.

Betrayal co-starring Liev Schreiber and John Slattery marked Juliette Binoche's Broadway debut and saw her nominated for a Best Actress Tony Award.