In Praise of Folly is an essay written in Latin in 1509 by Desiderius Erasmus of Rotterdam and first printed in 1511. Inspired by Italian humanist Faustino Perisauli's De Triumpho Stultitiae, it is a satirical attack on superstitions and other traditions of European society as well as on the western Church.

Erasmus revised and extended the work, which he originally wrote in the space of a week while sojourning with Sir Thomas More at More's estate in Bucklersbury. In Praise of Folly is considered one of the most notable works of the Renaissance and played an important role in the beginnings of the Protestant Reformation.