Religion in France is diverse, with the largest religious group being Christianity. A very significant part of the population is not religious, and significant minorities profess Islam and other religions. Freedom of religion and freedom of thought are warranted by the legacy of the 1789 Declaration of the Rights of Man and of the Citizen, and by the principle of laïcité (or "freedom of conscience") enforced by the 1880s Jules Ferry laws and the 1905 law on the Separation of the Churches and the State. Catholicism was the major religion in the realm of the French monarchy for more than a millennium, and it also held the role of state religion; the monarchy had such close ties to the Roman papacy that France was called the "eldest daughter of the Church" (French: fille aînée de l'Église).

A series of censuses throughout the 19th century included a question on the religious affiliation of the respondents, with the results depicted in the table below.

More recently, there has been a series of sample surveys used to determine the religious composition of the population, with the most official ones carried out by the Eurostat, the statistical agency of the European Union, and the government of France. A summary of the statistics is included in the table below. The most recent estimates show a growing percentage of people unaffiliated with an organized religion, particularly with the youngest demographics, while Christianity remains the most followed religion.

According to a national ten-year survey of 2020 held by the National Institute of Statistics and Economic Studies (INSEE), 34% of the French population between the age of 18 and 49 (and thus excluding the youngest and oldest demographics) adhered to Christianity, of whom approximately 25% were Catholics and 9% other Christians (without further specification; it may include nondenominational Christianity as well as various branches of Protestantism, Eastern Christianity, and other denominations of the religion); at the same time, 11% of the French population adhered to Islam, 0.5% to Buddhism, 0.5% to Judaism, and smaller negligible fractions to other religions (Hinduism and Sikhism, amongst others). At the same time, 53% of the sample declared that they had no religion. Between 2010 and 2020, the INSEE recorded a decline of Catholicism for the same demographics (between 18 and 49 years of age) from 43% to 25%, a growth of nondenominational and other denominations of Christianity from 2.5% to 9%, a growth of Islam from 8% to 11%, and of non-religious people from 45% to 53%, while the proportion of other religions remained stable.

France guarantees freedom of religion as a constitutional right, and the government generally respects this right in practice. Because of a long history of anticlericalism, the state cut its institutional ties with the Catholic Church in 1905 and made a strong promise to keep the public sector free of religion.

Catholicism is the largest religion in France. During the pre-1789 Ancien Régime, France was traditionally considered the Church's eldest daughter, and the King of France always maintained close links to the Pope. However, the "Gallicanism" policy meant that the king selected bishops.

A strong Protestant population resided in France, primarily of Reformed confession. The government usually opposed this but at times, tolerated more. This suppression continued throughout the 16th century, culminating in the St. Bartholomew's Day massacre, until the 1598 Edict of Nantes issued by Henry IV.

For the first time, the state considered Huguenots something other than mere heretics. The Edict of Nantes thus opened a path for secularism and tolerance. In addition to offering general freedom of conscience to subjects, the edict offered many specific concessions to the Huguenots, including amnesty and the reinstatement of their civil rights, the right to work for the state or in any field, and to bring grievances directly to the king.