The term problem plays is applied to the three plays William Shakespeare wrote between the last of his pure comedies (Twelfth Night) and the first of his pure tragedies (Othello) They are All's Well That Ends Well, Measure for Measure, Troilus and Cressida. The term was coined by critic F.S. Boas in Shakespeare and his Predecessors (1896).

Boas applied the term to plays in which the resolution of the themes and debates seems inadequate, and in the final act the deliverance of justice and completion one expects does not occur. Other definitions have followed, but all center on the fact that the plays cannot be easily assigned to the traditional categories of comedy or tragedy.

Critic Harold Bloom has suggested that this sequence of plays marked a psychological turning point for Shakespeare, during which he lost interest in the romantic comedies he had specialized in and turned towards the darker worlds of Othello, King Lear and Macbeth.

The three plays are also referred to as the dark comedies, since despite ending on a generally happy note for the characters concerned, the darker, more profound issues raised cannot be fully resolved or ignored.

Some scholars treat Hamlet, which was probably written either just before or just after Twelfth Night, as a problem play as well. The term is also applied to other odd plays from various points in his career, which reflects on the fact that this term has always been somewhat vaguely defined.