Michel is the protagonist and the narrator of the novel’s main narrative. He grows up in a middle-class Protestant family in France and at first has a sheltered experience of the world, devoting himself to the study of classics, Greek and Roman civilization. His personality and his perspective on life change dramatically after he marries Marceline, journeys with her to North Africa, and contracts tuberculosis. While recovering from his illness, Michel develops a philosophy that he must live in the present moment and pursue sensual pleasure, whether through pleasurable scenes in nature or sexual pleasure. He rejects the constraints that society places on him, losing interest in his career and socializing with his peers in favor of pursuing hedonistic pursuits with working-class men. He also undergoes a physical transformation that mirrors his philosophical one, becoming strong and fit in his pursuit of health and a connection with nature.

Throughout the book, Michel feels conflicted about neglecting his wife so that he can live a more authentic life. Gide implies throughout the narrative that Michel is gay and is interested in boys. For most of the narrative, Michel represses his sexual interest in boys, but he admits this attraction to his friends at the end of his narrative.