The Relapse, or Virtue in Danger, is a 1696 Restoration comedy written by English dramatist Sir John Vanbrugh. It is the author’s most successful play, and it is an ironic sequel to Love's Last Shift, or The Fool in Fashion, which was written earlier that year by playwright Colley Cibber. As such, The Relapse contains many of the same themes and characters as Love's Last Shift. Both plays were written in response to the Puritan movement, which took place in England at the start of the seventeenth century.

Cibber’s play tells the story of an immoral womanizer named Loveless and his cunning and virtuous wife, Amanda, who decides to disguise herself as a courtesan and seduce her own husband, so that he can repent and stop his unfaithfulness. Impressed with her wit, Loveless reforms and swears to remain faithful to his wife.

Vanbrugh’s play, however, describes how Loveless doesn’t keep his promise and relapses back to infidelity by romantically pursuing the beautiful widow Berinthia. Berinthia's ex-lover, Worthy, tries to seduce Amanda by telling her of her husband’s unfaithfulness, but Amanda refuses his advances and remains loyal to her unworthy husband. This is the main plot of the story.

An interesting element of the play is the fact that it contains a sub-plot, which is much more entertaining and humorous than the primary plot. In it, Lord Foppington, the former Sir Novelty Fashion from Cibber’s play, has acquired his nobility by purchasing the title of Lord, and he is now looking for a rich heiress to be his wife. However, his penniless younger brother, Tom, decides to disguise himself as Novelty and secretly marry Hoyden, the wealthy Sir Tunbelly Clumsy’s daughter. Thus, when Lord Foppington arrives for his bride, chaos and confusion ensue. Many critics argue that this sub-plot might actually be more important than the original plot of The Relapse.

Vanbrugh’s play was praised for its light and witty narrative, its bold opinions on attraction, love, marriage and (in)fidelity, and its well-developed characters, who represent the men and women in a sanctimonious community that believed that marriage was the answer to all romantic and sexual problems, including adultery.