Theophrastus redivivus is an anonymous Latin-language book published on an unknown date sometime between 1600 and 1700. The book has been described as "a compendium of old arguments against religion and belief in God" and "an anthology of free thought." It comprises materialist and skeptical treatises from classical sources as Pietro Pomponazzi, Lucilio Vanini, Michel de Montaigne, Machiavelli, Pierre Charron, and Gabriel Naudé.
Theophrastus redivivus is famous for proclaiming that all the great philosophers, including the eponymous Theophrastus, have been atheists; religions are contrived works of men; there is no valid proof for the existence of gods, and those who claim experience of a god are either disingenuous or ill. However, unlike the Treatise of the Three Impostors, another anti-religious work published around the same time, Theophrastus redivivus was never mentioned by the Age of Enlightenment philosophers and thinkers of the next century, despite being one of the first explicitly anti-religious works ever published in modern Europe.
Today, only four copies are known to survive: one in the French National Library in Paris (donated by Claude Sallier in 1741, who allegedly bought it from the auction of Karl Heinrich von Hoym's estate in August 1738), two in the Austrian National Library in Vienna, and one owned by a Belgian professor.
The manuscript shares its title with another, printed book also titled Theophrastus redivivus, which was published in Frankfurt by an Elias Johann Hessling in 1659. The 1659 book, written in German and defending the Swiss German Renaissance scientist and occultist Paracelsus, has no connection to the anonymous work. It is unknown which work predates the other, and why the two books share the same title; neither works mentions the other.