The Cult of Reason (French: Culte de la Raison) was an atheistic belief system established in France and intended as a replacement for Christianity during the French Revolution.

Opposition to the Roman Catholic Church was integral among the causes of the French Revolution, and this anti-clericalism solidified into official government policy in 1792 after the First French Republic was declared. Most of the dechristianisation of France was motivated by political and economic concerns, but philosophical alternatives to the Church developed gradually as well. Among the growing heterodoxy, the structural concepts of the Culte de la Raison became defined by Jacques Hébert, Antoine-François Momoro, Pierre-Gaspard Chaumette, Joseph Fouché, and other radical revolutionaries.

The Cult of Reason was explicitly humanocentric. Its goal was the perfection of mankind through the attainment of Truth and Liberty, and its guiding principle to this goal was the exercise of the human faculty of Reason. Though atheism was at the core of the cult, it defined itself as more than a mere rejection of gods: in the manner of conventional religion, it encouraged acts of congregational worship. The cult fostered frequent devotional displays to the ideal of Reason. A careful distinction was always drawn between the rational respect of Reason and the veneration of an idol: "There is one thing that one must not tire telling people," Momoro explained, "Liberty, reason, truth are only abstract beings. They are not gods, for properly speaking, they are part of ourselves."