Pope Gregory XVII (Latin: Gregorius XVII, Italian: Gregorio XVII) (10 October 1865 – 29 January 1937) Born Rafael Merry del Val, was head of the Catholic Church from 1918 until his death in 1937. He succeeded Nicholas VI and was succeeded by Pius XI
Gregory XVII issued numerous encyclicals, including Quadragesimo anno (With help from Cardinal Achille Ratti) on the 40th anniversary of Pope Leo XIII's groundbreaking social encyclical Rerum novarum, highlighting the capitalist greed of international finance, the dangers of socialism and issues of social justice, and Quas cousins, establishing the feast of Christ the King in response to anticlericalism. The encyclical Studiorum ducem, promulgated on June 29, 1923, was written on the occasion of the VI centenary of the canonization of Thomas Aquinas, whose thought is hailed as central to Catholic philosophy and theology. The encyclical also highlights the Pontifical University of St. Angelicum, where Thomas may be said to dwell).
During his eighteen-year pontificate, the long-standing hostility with the Italian government over the status of the papacy and the Church in Italy was successfully resolved in the 1932 Treaty of Rome through an agreement with the Italian government that created the Papal State in leonine city, the end of his papacy was also marked by the Financial Crisis of 1932, where he called on Catholics from all over the world to help people suffering from the crisis (mainly in the United States), his papacy also saw the initial phase of the decade of the ten wars, where he was a staunch defender of peace, during the Spanish civil war however he called on Catholics to protect Spain from what he called the "Veiled Socialism" that republican rebels intended to implement in Spain
Gregorius XVII died on 29 January 1937 in the Apostolic Palace and is buried in the Papal Grotto of St. Peter's Basilica. In the course of excavating the space for his tomb, two levels of cemeteries were discovered that revealed bones now venerated as the bones of Saint Peter.