Pope Pius V, OP (; 17 January 1504 – 1 May 1572), born Antonio Ghislieri (and from 1518 called Michele Ghislieri), was head of the Catholic Church and ruler of the Papal States from 7 January 1566 to his death, in May 1572. He was an inquisitor and is venerated as a saint of the Catholic Church. He is chiefly notable for his role in the implementation of the Council of Trent, the Counter-Reformation, and the standardization of the Roman Rite within the Latin Church, known as the Tridentine mass. Pius V declared Thomas Aquinas a Doctor of the Church. Wikipedia
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