Roman Catholicism has long been the main religion of Spain,and although it no longer has official status by law,in all public schools in Spain students have to choose either religion or ethics and Catholic is the only religion officially taught although in some schools there are large numbers of Muslim students together. According to a July 2009 study by the Spanish Center of Sociological Research about 73% of Spaniards self identify as Catholics, 2% other faith, and about 22% identify with no religion. Most Spaniards do not participate regularly in religious services. This same study shows that of the Spaniards who identify themselves as religious, 58% hardly ever or never go to church, 17% go to church some times a year, 9% some time per month and 15% every Sunday or multiple times per week.

But according to a December 2006 study, 48% of the population declared a belief in a supreme being, while 41% described themselves as atheist or agnostic. Altogether, about 22% of the entire Spanish population attends religious services at least once per month. Though Spanish society has become considerably more secular in recent decades, the influx of Latin American immigrants, who tend to be strong Catholic practitioners, has helped the Catholic Church to recover.

Santiago de Compostela Cathedral (A Coruña), the destination of the Way of St. James

Protestant churches have about 1,200,000 members.There are about 105,000 Jehovah's Witnesses. The Church of Jesus Christ of Latter day Saints has approximately 46,000 adherents in 133 congregations in all regions of the country and has a temple in the Moratalaz District of Madrid.

The recent waves of immigration have also led to an increasing number of Muslims, who number approximately one million in Spain. Presently, Islam is the second largest religion in Spain, accounting for approximately 2.3% of the total population.After their expulsion in 1492, Muslims did not live in Spain for centuries. Late 19th-century colonial expansion in northwestern Africa gave a number of residents in Spanish Morocco and Western Sahara full citizenship. Their ranks have since been bolstered by recent immigration, especially from Morocco and Algeria.

Judaism was practically non existent in Spain from the 1492 expulsion until the 19th century, when Jews were again permitted to enter the country. Currently there are around 62,000 Jews in Spain, or 0.14% of the total population. Most are arrivals in the past century, while some are descendants of earlier Spanish Jews. Approximately 80,000 Jews are thought to have lived in Spain on the eve of the Spanish Inquisition.Currently, Jews of Sephardic origin are given preferential status in the acquisition of Spanish citizenship.