What is the most popular religion in Spain?

Roman Catholicism is by far the most popular religion in the country of Spain. Over 90 percent of the entire Spanish population is Roman Catholic, as of 2014.

Spain is among the 10 most Catholic countries in the world. Some countries that have a greater total number of Catholics but not necessarily a higher percentage include the United States, Italy, France, Brazil and Colombia. Brazil is the country with the highest number of Catholics in the world, as of 2014. However, Brazil's population percentage of Roman Catholics is less than 70 percent.

Spain is estimated to have a total population of over 47.7 million people, as of 2014, and has the 29th greatest population in the world.