Pope Saint Pius X (2 June 1835 – 20 August 1914), born Giuseppe Melchiorre Sarto, was Pope from 4 August 1903 to his death in 1914. He was canonized in 1954. Pius X is known for vigorously opposing modernist interpretations of Catholic doctrine, promoting traditional devotional practices and orthodox theology. His most important reform was to order the codification of the first Code of Canon Law, which collected the laws of the Church into one volume for the first time. He was also considered a pastoral pope, in the sense of encouraging personal holiness, piety and a daily lifestyle reflecting deep Christian values. He was born in the town of Riese, which would later append "Pio X" (Pius X's name in Italian) to the town's name. Pius X was particularly devoted to the Blessed Virgin Mary under the specific title of Our Lady of Confidence; his papal encyclical Ad diem illum expresses his desire through Mary to renew all things in Christ, which he had defined as his motto in his first encyclical. Pius X believed that there was no surer or more direct road than by the Virgin Mary to achieve this goal. Pius X was the only pope in the 20th century with extensive pastoral experience and implementation at the parish level, which led him to favor the use of the vernacular language in teaching catechesis, while the encouragement for frequent reception of holy communion became a lasting innovation of his papacy. His immediate predecessor, Pope Leo XIII, had actively promoted a synthesis between the Catholic Church and secular culture; faith and science; and divine revelation and reason. Pius X defended the Catholic faith against popular 19th-century attitudes and views such as indifferentism and relativism which his predecessors had warned against as well. He followed the example of Leo XIII by promoting Thomas Aquinas and Thomism as the principal philosophical method to be taught in Catholic institutions. Pius X vehemently opposed modernism, which claimed that Roman Catholic dogma should be modernized and blended with nineteenth-century philosophies. He viewed modernism as an import of secular errors affecting three areas of Roman Catholic belief.

Personally, Pius X combined within himself a strong sense of compassion, benevolence and poverty, but also stubbornness and a certain stiffness. He wanted to be pastoral in the sense that he was the only pope in the 20th century who gave Sunday homily sermons in the pulpit every week. After the 1908 Messina earthquake he filled the Apostolic Palace with refugees, long before the Italian government acted. He rejected any kind of favours for his family; his brother remained a postal clerk, his favourite nephew stayed on as village priest, and his three sisters lived together close to poverty in Rome. He often referred to his own humble origins, taking up the causes of poor people. I was born poor, I have lived poor, and I wish to die poor. During his papacy, some of the world-renowned Marian images were granted a Canonical Coronation, namely the Our Lady of Aparecida, Our Lady of the Pillar, Our Lady of the Cape, Our Lady of the Rosary of Chiquinquirá, Our Lady of Gaverland (Belgium), Our Lady of San Juan de los Lagos, the Our Lady of La Naval de Manila and the Immaculate Conception within the Sala della Immacolata inside today's Vatican museums were granted its prestigious honors..

Considered a holy person by many, public veneration of Pope Pius X began soon after his death. Numerous petitions resulted in an early process of beatification which started in the 1920s, and which resulted in his canonization on 29 May 1954. The Society of Saint Pius X, a Traditionalist Catholic group, is named in his honor. A gigantic statue of him is enshrined within Saint Peter's Basilica, while the town of his birthplace was also renamed after his canonization.