Religion in Austria is predominantly Christianity, adhered to by 68.2% of the country's population according to the 2021 national survey^{[lower-alpha 1]} conducted by Statistics Austria.^[1] Among Christians, 80.9% were Catholics, 7.2% were Orthodox Christians (mostly belonging to the Eastern Orthodox Church), 5.6% were Protestants, while the remaining 6.2% were other Christians, belonging to other denominations of the religion or not affiliated to any denomination.^[1] In the same census, 8.3% of the Austrians declared that their religion was Islam, 1.2% declared to believe in other non-Christian religions (including Buddhism, Hindusim, Judaism and others), and 22.4% declared they did not belong to any religion, denomination or religious community.^[1]

According to church membership data, in 2021 53.9% of the population were Roman Catholics^[2] and 3.0% adhered to Protestant churches.^[3]

Austria was historically a strongly Catholic country, having been the centre of the Habsburg monarchy (1273–1918) which championed Roman Catholicism.^[4] Although in the 16th century many Austrians converted to Protestantism, Lutheranism in particular, as the Protestant Reformation (begun in 1517) was spreading across Europe, the Habsburgs enacted measures of Counter-Reformation as early as 1527 and harshly repressed Austrian Protestantism, albeit a minority of Austrians remained Protestant.^[4] A few decades after the fall of the Habsburg monarchy at the end of the World War I, and the transformation of Austria into a federal republic, at least since the 1970s there has been a decline of Christianity (with the exception of Orthodox churches) and a proliferation of other religions, a process which has been particularly pronounced in the capital state of Vienna.^[5]

Between the censuses of 1971 and 2021, Christianity declined from 93.8% to 68.2% of the Austrian population (Catholicism from 87.4% to 55.2%, and Protestantism from 6% to 3.8%, while Orthodox Christianity grew from 2.2% to 4.9% between 2001 and 2021).^[1] During the same timespan, Islam grew from being the religion of 0.2% to 8.3% of the Austrian population, and the proportion of people neither affiliating with nor belonging to any religion grew from 4.3% to 22.4%.^[1]

The Protestant Reformation spread from northern Germany to Austria. By the Council of Trent in 1545, almost half of the Austrian population had converted to Lutheranism, while a minority also endorsed Calvinism. Eastern Austria was more affected by this phenomenon than western Austria. After 1545, Austria was recatholicized in the Counter Reformation. The Habsburgs imposed a strict regime to restore the influence of the Catholic Church among Austrians and their campaign proved successful. The Habsburgs for a long time viewed themselves as the vanguard of Catholicism, while all the other Christian confessions and religions were repressed.

In 1775, Maria Theresa gave official permission to the Mechitarist Congregation of the Armenian Catholic Church to settle in the Habsburg Empire.

In 1781, in the era of Austrian enlightenment, Emperor Joseph II issued a Patent of Tolerance for Austria that allowed other confessions a limited freedom of worship. Religious freedom was declared a constitutional right in Cisleithania after the Austro-Hungarian Ausgleich in 1867, thus paying tribute to the fact that the monarchy was home to numerous religions besides Catholicism such as Greek, Serbian, Romanian, Russian, and Bulgarian Orthodox Christians (Austria neighboured the Ottoman Empire for centuries), both Calvinist and Lutheran Protestants, and Jews. In 1912, after the annexation of Bosnia Hercegovina in 1908, Islam was officially recognised in Austria.^[6]

The Austrian Jewish community of 1938—Vienna alone counted more than 200,000—was reduced to around 4,500 during the Second World War, with about 65,000 Jewish Austrians killed in the Holocaust and 130,000 emigrating.^[7] The large majority of the current Jewish population are post-war immigrants, particularly from eastern Europe and central Asia (including Bukharan Jews).^[8] Buddhism was legally recognised as a religion in Austria in 1983.^[9]

Austria was greatly affected by the Protestant Reformation, to a point where a significant part of the population became Protestant. Lutheranism was the most successful Protestant confession; that was the case among other German-speaking populations across the Holy Roman Empire and Austria was indeed one of them. Calvinism did not receive that much support. The prominent position of the Habsburgs in the Counter-Reformation, however, saw Protestantism all but wiped out beginning in 1545, restoring Catholicism as the dominant religion once more.

The significant Jewish population (around 200,000 in 1938), mainly residing in Vienna, was reduced to just a couple of thousand through mass emigration in 1938 (more than 2/3 of the Jewish population emigrated from 1938 until 1941), and the following Holocaust during the Nazi period. Immigration in more recent years, primarily from Turkey and the former Yugoslavia, has led to an increased number of Muslims and Serbian Orthodox Christians.^[10] As in other European countries, there has been a growth of Pagan movements in Austria in recent years.

In 2023, the country was scored 3 out of 4 for religious freedom;^[20] in 2021, the government established a new staff unit in the fight against antisemitist sentiment and violence.

• Buddhism in Austria
• Catholic Church in Austria
• Old Catholic Church of Austria
• Hinduism in Austria
• Islam in Austria
• History of the Jews in Austria
• Religions by country
• Freedom of religion in Austria