Pope Pius X was head of the Catholic Church from 4 August 1903 to his death in August 1914. Pius X is known for vigorously opposing modernist interpretations of Catholic doctrine, and for promoting liturgical reforms and scholastic theology. He initiated the preparation of the 1917 Code of Canon Law, the first comprehensive and systemic work of its kind. He is venerated as a saint in the Catholic Church. The Society of Saint Pius X, a traditionalist Catholic fraternity formed decades after his death, is named after him.

Modernism in the Catholic Church describes attempts to reconcile Catholicism with modern culture, specifically an understanding of the Bible and Catholic tradition in light of the historical-critical method and new philosophical and political developments of the late 19th and early 20th centuries.