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 leader 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,