Lady Audley's Secret is a sensation novel by Mary Elizabeth Braddon published in 1862. It was Braddon's most successful and well-known novel. Critic John Sutherland (1989) described the work as "the most sensationally successful of all the sensation novels". The plot centres on "accidental bigamy" which was in literary fashion in the early 1860s. The plot was summarised by literary critic Elaine Showalter (1982): "Braddon's bigamous heroine deserts her child, pushes husband number one down a well, thinks about poisoning husband number two and sets fire to a hotel in which her other male acquaintances are residing". Elements of the novel mirror themes of the real-life Constance Kent case of June 1860 which gripped the nation for years. Braddon's second 'bigamy' novel, Aurora Floyd, appeared in 1863. Braddon set the story in Ingatestone Hall, Essex, inspired by a visit there. There have been three silent film adaptations, one UK television version in 2000, and three minor stage adaptations.

The sensation novel, also sensation fiction, was a literary genre of fiction that achieved peak popularity in Great Britain in the 1860s and 1870s, centering taboo material shocking to its readers as a means of musing on contemporary social anxieties.