The Spanish Prisoner is a confidence game dating back to at least the 17th century. In its original form, the confidence artist tells his victim (the mark) that he is in correspondence with a wealthy person of high estate who has been imprisoned in Spain under a false identity. The alleged prisoner cannot reveal his identity without serious repercussions, and is relying on the confidence artist to raise money to secure his release. The confidence artist offers to let the mark supply some of the money, with a promise that he will be rewarded generously when the prisoner returns. However, once the mark has turned over his money, he learns that further difficulties have arisen, requiring more money, until the mark is cleaned out and the game ends.

Key features of the Spanish Prisoner are the emphasis on secrecy and the trust the confidence artist is placing in the mark not to reveal the prisoner's identity or situation. The confidence artist will often claim to have chosen the mark carefully based on his reputation for honesty and straight dealing, and may appear to structure the deal so that the confidence artist's ultimate share of the reward will be distributed voluntarily by the mark.

Modern variants of the Spanish Prisoner include the advance fee fraud, in which a valuable item must be ransomed from a warehouse, crooked customs agent, or lost baggage facility before the authorities or thieves recognize its value, and the Nigerian money transfer fraud – another type of advance fee fraud – in which a self-proclaimed relative of a deposed African dictator offers to transfer millions of ill-gotten dollars into the bank account of the mark in return for small initial payments to cover bribes and other expenses.

The film The Spanish Prisoner, written and directed by David Mamet, includes such a confidence trick as part of the plot, as does his other film about con men, House of Games.