Simplicius Simplicissimus (German: Der abenteuerliche Simplicissimus Teutsch) is a picaresque novel of the lower Baroque style, written in 1668 by Hans Jakob Christoffel von Grimmelshausen and probably published the same year (although bearing the date 1669). Inspired by the events and horrors of the Thirty Years' War which devastated Germany from 1618 to 1648, it is regarded as the first adventure novel in the German language and the first German novel masterpiece.

The full subtitle is "The account of the life of an odd vagrant named Melchior Sternfels von Fuchshaim: namely where and in what manner he came into this world, what he saw, learned, experienced, and endured therein; also why he again left it of his own free will."

The novel is told from the perspective of its protagonist Simplicius, a rogue or picaro typical of the picaresque novel, as he traverses the tumultuous world of the Holy Roman Empire during the Thirty Years' War. Raised by a peasant family, he is separated from his home by foraging dragoons and is adopted by a hermit living in the forest, who teaches him to read and introduces him to religion. The hermit also gives Simplicius his name because he was so simple that he did not know what his own name was. After the death of the hermit, Simplicius must fend for himself. He is conscripted at a young age into service, and from there embarks on years of foraging, military triumph, wealth, prostitution, disease, bourgeois domestic life, and travels to Russia, France, and to an alternative world inhabited by mermen. The novel ends with Simplicius turning to a life of hermitage himself, denouncing the world as corrupt.