Atlantis: The Antediluvian World is a pseudoarchaeological book published in 1882 by Minnesota populist politician Ignatius L. Donnelly.

Donnelly considered Plato's account of Atlantis as largely factual and suggested that all known ancient civilizations were descended from this lost land through a process of hyperdiffusionism.

Much of Donnelly's writing, especially with regard to Atlantis as an explanation for similarities between ancient civilizations of the Old and New Worlds, was inspired by the publications of Charles Étienne Brasseur de Bourbourg and the fieldwork of Augustus Le Plongeon in the Yucatan.

With his book he states that he is trying to prove thirteen distinct hypotheses:[2] In 1883, a sequel or companion, Ragnarok: The Age of Fire and Gravel, was published.

Donnelly's work on Atlantis inspired books by James Churchward on the lost continent of Mu, also known as Lemuria.