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Religion

At the beginning of the twentieth century, Paris was the largest Catholic city in the world. French census data does not contain information about religious affiliation. In a 2011 survey by the Institut français d'opinion publique (IFOP), a French public opinion research organisation, 61 percent of residents of the Paris Region (Île-de-France) identified themselves as Roman Catholic. In the same survey, 7 percent of residents identified themselves as Muslims, 4 percent as Protestants, 2 percent as Jewish and 25 percent as without religion.

According to the INSEE, between 4 and 5 million French residents were born, or had at least one parent born, in a predominantly Muslim country, particularly Algeria, Morocco and Tunisia. An IFOP survey in 2008 reported that, of immigrants from these predominantly Muslim countries, 25 percent went to the mosque regularly. 41 percent practised the religion, and 34 percent were believers, but did not practice the religion. In 2012 and 2013, it was estimated that there were almost 500,000 Muslims in the City of Paris, 1.5 million Muslims in the Île-de-France region and 4 to 5 million Muslims in France.

In 2014, the Jewish population of the Paris Region was estimated to be 282,000, the largest concentration of Jews in the world outside of Israel and the United States.