The Birthday Party is the second play by Harold Pinter. Taken at face value, the play concerns Stanley, a failed piano player, who lives in a boarding house (run by Meg and Petey), in a British seaside town. On his birthday, Stanley is visited by two men, Goldberg and McCann. A supposedly innocent birthday party quickly becomes a nightmare.

The Birthday Party is a reaction to the theatrical trends of the time, displaying many traits of Theatre of the Absurd. Time, place and identity are ambiguous and fluid, and even language breaks down. Some or all of the exposition information given by the characters may be erroneous. In Act I, Stanley describes his career saying "I've played the piano all over the world. All over the country" and then after a pause simply "I once gave a concert." Although Meg claims that her house is a "boarding house", Stanley denies it and there is no mention in the stage directions of it being so. Meg acts as if she is running a boarding house, but even her husband seems surprised that she already has a room prepared for guests. All the place names suggest that the house is in a seaside town on the south coast of London.¹ Stanley denies that it is his birthday several times throughout the play, but Meg claims he doesn't know that it's his birthday because she's keeping it a secret. McCann claims to have no knowledge of Stanley or Maidenhead (Stanley's hometown), but Goldberg later names two businesses that Stanley used to frequent, which connects him to Maidenhead. The past is made more confusing by the question of identity: Goldberg is called "Nat," but in the past he was called "Simey" and also "Benny"; McCann is also referred to as "Seamus" and "Dermot" (though these may simply be stereotypical Irish appellations). Although Stanley at one point of the birthday party begins to strangle Meg, she has no memory of it the next morning (but, then again, she was drinking a lot throughout the previous evening's party!).

Although it is now one of Pinter's best-known plays, The Birthday Party was a commercial failure when originally performed in the West End in 1958.