Poland remains one of Europe's most religiously observant Catholic-majority countries, around 85 to 90 percent Catholic by formal affiliation per most estimates including Pew Research's Religious Composition of the World, 2010-2020, with small Orthodox Christian, Protestant and religiously unaffiliated minorities, though church attendance has declined notably among younger Poles in recent years.
Poland adopted Christianity in 966 CE under Duke Mieszko I, an event traditionally dated to his baptism and treated as the founding moment of the Polish state itself, and Catholicism became deeply fused with Polish national identity over subsequent centuries, particularly through repeated partitions and foreign occupations in which the Church served as one of the few durable institutions of Polish culture and language.
Poland was historically home to Europe's largest Jewish community, whose roots trace to medieval royal invitations for Jewish settlement and whose Yiddish-speaking culture flourished for centuries before the Holocaust, in which Nazi Germany built its largest extermination camps, including Auschwitz-Birkenau and Treblinka, on occupied Polish soil, destroying the great majority of Poland's roughly three million Jews. Karol Wojtyla, elected Pope John Paul II in 1978 as the first non-Italian pope in over four centuries, is widely credited with galvanizing the Solidarity movement's peaceful challenge to Communist rule in the 1980s.