Demian: The Story of a Boyhood is a bildungsroman by Hermann Hesse, first published in 1919; a prologue was added in 1960. Demian was first published under the pseudonym "Emil Sinclair", the name of the narrator of the story, but Hesse was later revealed to be the author; the tenth edition was the first to bear his name.

Emil Sinclair is a young boy raised in a middle class home, amidst what is described as a Scheinwelt, a composite word meaning "world of illusion," so his entire existence can be summarised as a struggle between two worlds: the show world of illusion (related to the Hindu concept of maya) and the real world, the world of spiritual truth (see Plato's cave and dualism). Accompanied and prompted by his mysterious classmate and friend 'Max Demian', he detaches from and revolts against the superficial ideals of the world of appearances and eventually awakens into a realization of self.

Demian became a cult classic, especially among youth disillusioned after World War I. It foreshadows Hesse's later works like Siddhartha and Steppenwolf, which also explore self-liberation and existential quests.