Irreligion in Spain is a phenomenon that has existed since at least the 17th century.^[2] Secularism became relatively popular among rich people (although the majority of the lower classes were still very religious) in the late 19th and early 20th centuries, often associated with anti-clericalism and progressive, republican, anarchist or socialist movements.^[3]

During the Second Spanish Republic (1931–1936) Spain became a secular state, placing limitations on the activity of the Catholic Church and expelling the church from education. During the Spanish Civil War irreligious people were repressed by the Francoist side, while religion was largely persecuted among the republicans.

During the Francoist Spain period (1939–1975) irreligion was not tolerated, following the national-catholic ideology of the regime; Spanish citizens had to be Catholic by law, though this changed after the Second Vatican Council. Irreligious people could not be public workers or express their thoughts openly.

After the Spanish democratic transition (1975–1982), restrictions on irreligion were lifted.^[4] In the last decades religious practice has fallen dramatically and irreligion has grown in popularity.^[5]

According to a 2018 study by the Ferrer i Guàrdia Foundation, 27% of Spanish people are either atheist, agnostic or non-believers, with 49% of 18-24 year olds in one of those categories.^[6] A survey by Centro de Investigaciones Sociológicas in October 2014 showed that 67.8 percent of Spanish people would today describe themselves as Catholic, although only 16.9 percent of Spanish people attend mass at least once a month. 10.8% define themselves as atheist and a further 16.7% as non-believers.^[7][8] In 2008, several reports^{[citation needed]} indicated that as much as 60% of the population of Madrid and its metropolitan area identified as non-religious. According to a 2009 study, the 46% of Spaniards aged 18–24 declare themselves atheist or agnostic.^[9] In 2019, a study carried out by the CIS found that 48.9% of Spaniards aged 18–24 declared themselves atheist or agnostic, therefore becoming a majority over those who declared themselves as religious.^[10]

The close alliance of Francoist Spain and the Catholic Church is said to have had a considerable amount of influence on the decline of religion in Spain.^[11] The prevalence of the Church on the people and the subsequent end of the Spanish State caused the Spanish to detach themselves from Catholicism as political coercion was relaxed.^[11] In the 16 years after the transition from a dictatorship to democracy, there was a significant drop in levels of religious practice. According to Miguel and Stanek, there was a 14% decrease in religious practice in Spain in just those 16 years, decreasing at an annual rate of −2.1%.^[11]

In 1966 Francoist Spain passed a law that freed other religions from many of their earlier restrictions, although it also reaffirmed the privileges of the Catholic Church.^[12] In 1978 the new Constitution confirmed the right of Spaniards to religious freedom and began disestablishing Catholicism as the state religion and declaring that religious liberty for non-Catholics is a government-protected right.^[12]

Freedom of ideology, religion, and worship is guaranteed, to individuals and communities with no other restriction on their expression than may be necessary to maintain public order as protected by law.^[8]

No one may be compelled to make statements regarding his or her ideology, religion, or beliefs.^[8]

There is no state religion. The public authorities shall take into account the religious beliefs of Spanish society and shall consequently maintain appropriate cooperative relations with the Catholic Church and other denominations.^[8]

The process of secularization was already clearly recognizable by the end of the eighteenth century. The depth, influence, and continuity of Spain's liberal and democratic traditions are particularly important in trying to understand the values connected with the ideals of tolerance and religious freedom. Seen in this light, it becomes clear why Spain in particular was one of the first countries in the world to introduce women's rights and why the divorce law of the Second Republic (1931–1936) was one of the most progressive ever passed. It is the foundation for today's law on same-sex marriage, which has led to conflict recently.^[8]

Although more than 19 out of every 20 Spaniards were baptized Catholics, the secularization process has become more intense both on an institutional level as well as in the everyday lives of the people. It is argued that in return for the subsidy that the Church receives, society receives the social, health, and educational services of tens of thousands of priests and nuns. Instead, a system was set up to allow citizens to delegate up to 10% of their pay check to the church so that it was no longer government funded.

There exists an inverse relationship between the level of education and the social significance of religion.^[11] By 1980, a study was conducted that showed the more educated a person was, the more likely he or she was to be irreligious.^[12] This is attributed to the Church's new self-restraint in politics. The church began accepting the need for separation of religion and the state.^[11]

• Religion in Spain

• Ateus de Catalunya
• L'Associació Valenciana d'Ateus i Lliurepensadors (AVALL)
• Ateos de Madrid
• Ateos de Albacete
• Asociación de Ateos y Librepensadores de Andalucía
• Ateneu Eclèctic I Liberal D'ateus I Agnóstics