Ordeal by Innocence is a detective fiction novel by Agatha Christie, first published in 1958. The story centers on the Argyle family, where Jacko Argyle is accused of murdering his adoptive mother, Rachel Argyle. Jacko maintains his innocence, but dies in prison while serving a sentence for the murder. His alibi failed when police could not find the man who had given Jacko a ride to the next town as the murder was happening.

Two years after Jacko's conviction and death, his alibi steps forward. Dr. Arthur Calgary had been out of the country during the trial and only heard news of it upon his return. Certain that Jacko was innocent, Dr. Calgary takes it upon himself to investigate the past. When Dr. Calgary arrives with the proof that confirms Jacko's innocence, it is too late—Jacko died behind bars following a bout of pneumonia.

In the original 1958 novel, the killer of Rachel Argyll is revealed to be the housekeeper Kirsten Lindstrom. She murdered Rachel on behalf of Rachel's adopted son Jack Argyll, and then bumped off Philip Durrant (and stabbed Tina Argyll) in an attempt to keep the secret. In the BBC series of Ordeal By Innocence, the killer of Rachel Argyll is revealed to be her husband, Leo, played by Bill Nighy.