A plot device is an object or character in a story whose sole purpose is to advance the plot of the story, or alternatively to overcome some difficulty in the plot.

A contrived or arbitrary plot device may annoy or confuse the reader, causing a loss of the suspension of disbelief. However a well-crafted plot device, or one that emerges naturally from the setting or characters of the story, may be entirely accepted, or may even be unnoticed by the audience.

Many stories, especially in the fantasy genre, feature an object or objects with some great power. Often what drives the plot is the hero's need to find the object before the villain and use it for good rather than evil, or if the object has been broken by the villains, to retrieve each piece that must be gathered from each antagonist to restore it, or, if the object itself is evil, to destroy it. In some cases destroying the object will lead to the destruction of the villain. In the Indiana Jones film series, Jones is always on the hunt for some mystical artifact. In Raiders of the Lost Ark, he is trying to retrieve the Ark of the Covenant; in Indiana Jones and the Last Crusade, Jones is on a search for the Holy Grail. This plot device dates back to the medieval Arabian Nights tale of "The City of Brass", in which a group of travellers on an archaeological expedition journey across the Sahara to find a brass vessel that Solomon once used to trap a jinn.