Jacques the Fatalist and his Master (French: Jacques le fataliste et son maître) is a philosophical novel by French writer and philosopher Denis Diderot, presumably written sometime between 1765 and 1780. It is largely presented in the form of a dialogue, mainly between the servant Jacques and his master, who is not given a name. The novel tells the tale of the eventful journey of Jacques and his master, as they travel through France, meet new characters, experience new adventures, and learn new stories.

The main theme of the novel is, naturally, the relationship between Jacques and his master. Along the way, Jacques tells the story of his life and his past loves, even though he is often interrupted by various characters and events. He speaks of a certain philosophy in which he believes: the idea that everything that happens to mankind and to all living beings, every decision that we make, no matter how whimsical, is predetermined from above, or from a higher deity. We are, essentially, slaves to our own fate and destiny. Many consider this to be characteristic of his determinism and even his fatalism, which explains the origin and the inspiration behind the title of the book. In contrast, Jacques’s master remains skeptical of his fatalism and is mostly passive throughout the novel.

Because of its dialogue form, the book is more often compared to a stage play than to a typical novel. The readers are given a certain amount of freedom to interpret the events and evaluate the characters, based on their own opinions. Through the humorous scenes, the repetitive interruptions of the dialogue and the conversation, and the numerous sub-stories of other characters, Diderot portrays the unpredictability of life and questions all understanding of free will and reality.

The novel received mixed reviews: it was mainly criticized for its allegedly nonreligious, inappropriate, and lewd narrative; however, it was praised (especially among German intellectuals) for its playful and entertaining storytelling, its picturesque and vivid scenery, and its accurate portrayal of eighteenth-century France. Thus, Jacques the Fatalist and His Master is considered one of the most interesting representations of Enlightenment philosophy in literature.