Religion in the Czech Republic was dominated by Christianity until at least the early 20th century. Since the 1620 Battle of White Mountain religious sphere was accompanied by a widespread anti-Catholic sentiment even when the whole population nominally belonged to the Catholic Church. Overall, Christianity has steadily declined since the early 20th century and today remains only a minority. The Czech Republic has one of the oldest least religious populations in the world. Ever since the 1620 Battle of White Mountain, the Czech people have been historically characterised as "tolerant and even indifferent towards religion". According to Jan Spousta, among the irreligious people, who form the vast majority of modern Czechs, not all are atheists; indeed there has been an increasing distancing from both Christian dogmatic and atheistic ideologies, and at the same time ideas from Far Eastern religions have become widespread.
Christianisation in the 9th and 10th centuries introduced Roman Catholicism. After the Bohemian Reformation, most Czechs (about 85%) became followers of Jan Hus, Petr Chel?ický and other regional Protestant Reformers. Taborites and Utraquists were major Hussite groups. During the Hussite Wars, Utraquists sided with the Catholic Church. Following the joint Utraquist--Catholic victory, Utraquism was accepted as a distinct form of Christianity to be practised in Bohemia by the Catholic Church while all remaining Hussite groups were prohibited. After the Reformation, some Bohemians went with the teachings of Martin Luther, especially Sudeten Germans. In the wake of the Reformation, Utraquist Hussites took a renewed increasingly anti-Catholic stance, while some of the defeated Hussite factions (notably Taborites) were revived. Bohemian Estates' defeat in the Battle of White Mountain brought radical religious changes and started a series of intense actions taken by the Habsburgs in order to bring the Czech population back to the Catholic Church. After the Habsburgs regained control of Bohemia, the whole population was forcibly converted to Roman Catholicism--even the Utraquist Hussites. All kinds of Protestant communities including the various branches of Hussites, Lutherans and Reformed were either expelled, killed, or converted to Roman Catholicism. Going forward, Czechs have become more wary and pessimistic of religion as such. A long history of resistance to the Catholic Church followed. It suffered a schism with the neo-Hussite Czechoslovak Hussite Church in 1920, lost the bulk of its adherents during the communist era and continues to lose in the modern, ongoing secularisation. Protestantism never recovered after the Counter-Reformation was introduced by the Austrian Habsburgs in 1620.
According to the 2011 census, 34.5% of the population stated they had no religion, 10.5% were Catholics, 1% Protestants, 0.9% members of other Christian churches, 6.8% were believers but not members of religions, while 0.7% were believers and members of other certain religions. 44.7% of the population did not answer the question about religion. From 1991 to 2001 the population's proportion of members of the Catholic Church decreased from 39.0% to 26.8%. Protestantism declined from 4% to 2%. Due to changes in the last 2011 census' categories, each category has seen a decrease: the proportion of people who have no religion declined from 59% to 34.5%, the Catholics declined from 26.8% to 10.3% and Protestants declined from 2% to 1%. People who didn't answer the optional question rose from 8.8% to 44.7%.
|- -Ruthenian Greek Catholic Church||9,307||0.1||12,149||0.1||32,862||0.4||7,030||0.1||7,675||0.1||9,883||0.1|
|-Evangelical Church of Czech Brethren||231,199||2.3||290,994||2.7||401,729||4.5||203,996||2.0||117,212||1.1||51,858||0.5|
|-Czechoslovak Hussite Church||523,232||5.2||779,672||7.3||946,813||10.6||178,036||1.7||99,103||1.0||39,229||0.4|
|-Silesian Evangelical Church of the Augsburg Confession||-||-||46,777||0.4||57,741||0.6||33,130||0.3||14,020||0.1||8,158||0.1|
|-German Evangelical Church||-||-||130,981||1.2||6,401||0.1||-||-||-||-||-||-|
|-Czech and Slovak Orthodox Church||9,221||0.1||24,488||0.2||50,365||0.6||19,354||0.2||22,968||0.2||20,533||0.2|
|-Christian churches not exactly stated||-||-||5,808||0.1||-||-||8,790||0.1||4,021||0.04||91,894||0.8|
|Believers identified with another certain religions||168,046||1.7||53,743||0.5||57,287||0.6||36,146||0.4||257,641||2.5||75,190||0.7|
|Believers not identified with a certain religion||-||-||-||-||-||-||-||-||-||-||705,368||6.8|
Christianity was the largest religion in the country, with virtually all Czechs being Christians until the 19th century. The Czechs gradually converted to Christianity from Slavic paganism between the 8th and the 10th century. Bo?ivoj I, Duke of Bohemia, baptised by the Saints Cyril and Methodius, was the first ruler of Bohemia to adopt Christianity as the state religion. Christianity has been on the decline since the 20th century and in 2011 only 12.6% of the Czechs declared to be Christians, of whom 10.5% were Catholics, 1% Protestants and 1.1% members of other Christian bodies. In 1921, 77.5% of the Czech population was Catholic, 7.7% belonged to the Czechoslovak Hussite Church that broke off the Catholic Church in 1920, 3.4% belonged to the Czech Brethren, 0.3% were other Protestants, 0.7% were religious Jews, 0.1% belonged to some other religious category, and a further 10.3% were irreligious.
The Catholic Church was the main form of Christianity historically practised by the Czechs, after their forced conversion under the Habsburgs, and throughout the 18th and 19th centuries. Catholicism was still the professed religion of 96.5% of the Czechs in 1910. A decline in the number of Czech Catholics began after World War I and the breakup of Austria-Hungary due to a popular anti-Austrian and anticlerical mass movement. During the Czechoslovak unification under a communist regime, most of the properties of the Church were confiscated by the government, although some were later returned. After the communist regime fell, 39.0% of Czechs were found to be Catholic in 1991, but the faith has continued to rapidly decline since. As of 2011 only 10.5% of the Czechs considered themselves Catholic, which is about the same as in Protestant-majority England.
In the 15th century, the religious and social reformer Jan Hus formed a movement later named after him. Although Hus was named a heretic and burnt in Constance in 1415, his followers seceded from the Catholic Church and in the Hussite Wars (1419-1434) defeated five crusades organised against them by the Holy Roman Emperor Sigismund. Petr Chel?ický continued with the Czech Hussite Reformation movement. During the next two centuries, most of Czechs were adherents of Hussitism.
After 1526 Bohemia came increasingly under Habsburg control as the Habsburgs became first the elected and then the hereditary rulers of Bohemia. The Defenestration of Prague and subsequent revolt against the Habsburgs in 1618 marked the start of the Thirty Years' War, which quickly spread throughout Central Europe. In 1620, the rebellion in Bohemia was crushed at the Battle of White Mountain, and the ties between Bohemia and the Habsburgs' hereditary lands in Austria were strengthened. The war had a devastating effect on the local population; the people were forced to convert to Catholicism.
Protestantism constitutes a 1% small minority in the country in the 2010s, with only 0.5% of the Czechs adhering to the Evangelical Church of Czech Brethren, 0.4% to the Czechoslovak Hussite Church, and 0.1% to the Silesian Evangelical Church of the Augsburg Confession. The Moravian Church, being historically tied to the region, is present too with a small number of members.
The 2001 census counted 6,817 registered Buddhists in the Czech republic. Most of the Vietnamese ethnic minority, which make up the largest immigrant ethnic group in the country, are adherents of Mahayana Buddhism. The Vietnamese mostly dwell in the cities of Prague and Cheb. Thein An Buddhist Temple in the northern province of Varnsdorf was the first Vietnamese-style temple to be consecrated in the Czech Republic, in January 2008. There are also ten Korean Buddhist temples in the Czech Republic, with three each in Prague and Brno.
Ethnic Czech Buddhists are otherwise mostly followers of Vajrayana Buddhism (Tibetan Buddhism). The Vajrayana practitioners are mainly centered on the Nyingma and Kagyu schools. The Karma Kagyu tradition has established about 50 centers and meditation groups. The Diamond Way tradition of Vajrayana Buddhism, founded and directed by Ole Nydahl is active in both the Czech Republic and Slovakia. A large temple of the school is going to be built in the city of Prague.
The revived native religion of the Slavs (Rodnovery in English, Rodnoví in Czech) has a presence in the Czech Republic. The largest organisation is the "Community of the Native Faith". There are also Wiccan followers, and one Kemetic group in the country, Per Kemet.
The Czech Republic is one of the least religious countries in the world. Vera Haberlová of STEM, for example, writes about 50% representation of atheists in Czech society. In doing so, however, it comes from simple inquiries to the question "Do you believe in God?", which also indicates a very simplistic evaluation, because a high percentage of respondents classified this way that also believe in some other "Higher Power." Summary group of non-believers in God was, According to STEM survey in June 1996 Represented 48.8% of the Czech population and in July 1998 it was 47.6%. In 1994 According to STEM called themselves atheists are 21.5% of persons aged 18 years and 20.3% of those aged 15-17 years, while a further 38.2%, respectively. 40.8% of people said they are not religious.
According to the results of the 2001 census 7% more men were without religion than women. The age group most likely to have no religion (74%) is young people 0-30 years old, the least likely (28%) is people aged 60+ years. When categorised by education, the higher the educational level achieved, the more people were to state they had no religion.
There is an organised group of atheists in the Czech Republic, the Civic Association of Atheists, a member of the international organisation of atheists Atheist Alliance International (AAI). Not all irreligious Czechs are atheists; many non-religious people have adopted ideas from Far Eastern religions.