Christianity is the main religion in Spain and the majority of the Spanish population is Catholic.  However, in the past decades, the Christian percentage has significantly declined and the Unaffiliated percentage has increased.  Law prevents the Spanish census from recording the religious affiliation of the population.

As per the estimates, 68% of the population identified as Christians. The majority of Christians are Catholics and other affiliations are less than a percent. Non-Christian faiths account for 3%, and the remaining 29% are classified as unaffiliated, which can mean agnostic, atheist, or “nothing in particular.” The vast majority of unaffiliated adults in Spain (86%) say they were raised as Christians. 

Other religions include Islam, Jews, Hinduism, Sikh, Buddhism, and other smaller faiths.

The recent waves of immigration, especially during and after the 2000s, have led to a fast-increasing number of Muslims. Nowadays, Islam is the second largest religion, but far behind Roman Catholicism and irreligion.

Jews in Spain form less than 0.2% of the overall population, somewhere between 13,000 and 50,000. They are primarily located in the cities of Barcelona, Madrid, and Málaga.

Hinduism first arrived in Spain through Sindhi immigrants through the British colony of Gibraltar in the early 20th century. There are about 40,000-50,000 Hindus in Spain, about 25,000 from India, 5,000 from Eastern Europe and Latin America, and 10,000 Spanish. There are also small communities of Hindus from Nepal and Bangladesh There are also about 40 Hindu temples/worship places in Spain.

According to an estimation from 2018, there are around 90,000 followers of Buddhism in Spain and a total number of around 300,000 adherents if sympathizers are included. There are also almost 300 centers for Buddhist practice in the country.

Smaller faiths include Paganism and Taoism.

Source: Pew Research Center and estimates