Thieves' World is a shared world fantasy series created by Robert Lynn Asprin in 1978. The original series comprised twelve anthologies, including stories by science fiction authors Poul Anderson, John Brunner, Andrew J. Offutt, C. J. Cherryh, Janet Morris, and Chris Morris.

Thieves' World is set in the city of Sanctuary at the edge of the Rankan Empire. The city is depicted as a place where many are downtrodden and where the invading Rankan gods and the Ilsigi gods they had ousted begin a struggle for dominance. As the series continues, additional invasions occur, and the city is taken over by the snake-worshipping Beysib as the Rankan empire collapses. Over time, a number of the characters in the series are revealed either to be the offspring of or otherwise blessed by various figures in the pantheons of the competing deities, and they discover or develop various powers as the series progresses.

First published in 1979, the series went on hiatus in 1989 after the twelfth anthology. In addition to the official anthologies, several authors published novels set in Thieves' World.

In 2002, Lynn Abbey, who co-edited several of the original anthologies, relaunched the series with the novel Sanctuary. It was followed by the anthologies Turning Points and Enemies of Fortune, which contain some returning authors and several new ones. Abbey also oversaw the republication of the original anthologies in omnibus editions.