Austria is historically and still predominantly Catholic, though the Catholic share has fallen substantially in recent decades to around 55 percent, with religiously unaffiliated residents now forming the second largest group at roughly a quarter of the population, alongside Muslim and Protestant minorities each in the low single digits, per estimates including Pew Research's Religious Composition of the World, 2010-2020.
Austria sat at the heart of the Holy Roman Empire and later the Habsburg monarchy, whose rulers styled themselves defenders of Catholicism through the Counter-Reformation, suppressing Protestant communities that had gained ground during the sixteenth-century Reformation and making Vienna a major center of Baroque Catholic art and architecture, exemplified by St Stephen's Cathedral and the Melk Abbey.
Vienna also hosted one of pre-Holocaust Europe's largest and most culturally significant Jewish communities, numbering around 200,000 before 1938, nearly all of whom were murdered, forced to emigrate or otherwise displaced following Austria's annexation by Nazi Germany that year, a community that never recovered its former scale or influence. Postwar Austria maintains a formal church-state partnership through concordat arrangements with the Catholic Church alongside a system recognizing other religious societies.