In Praise of Folly is an essay written in Latin in 1509 by Desiderius Erasmus of Rotterdam and first printed in 1511. The essay was inspired by De Triumpho Stultitiae, written by the Italian humanist Faustino Perisauli, born at Tredozio, near Forlì.
Erasmus revised and extended the work, which he originally wrote in the space of a week while sojourning with Sir Thomas More at Mores 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.