Pope Pius V (died 1572)

Pope Pius V, OP, born Antonio 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.

January 17 is the 17th day of the year in the Gregorian calendar; 348 days remain until the end of the year.