Antonio Ghislieri was born to a poor family in Piedmont and entered the Dominican Order at fourteen. A spare, sober man of ascetic life and severe judgement, he taught theology, served as inquisitor in Como and Bergamo, became bishop and cardinal, and was elected pope in 1566 — by acclamation of the reform party, against the influence of the Spanish.
His six-year pontificate completed and embedded the Council of Trent (1545–63). He promulgated the Roman Catechism (1566), the reformed Breviary (1568), and — supreme achievement — the Roman Missal (1570), which standardised the celebration of Mass throughout the Latin Church. The 'Tridentine Mass' as it would come to be called would remain essentially unchanged until 1969–70.
In foreign affairs he forged the Holy League — Spain, Venice, the Papal States, and several smaller Italian powers — against the Ottoman advance. He called for Rosary processions in every parish of Christendom on the day of battle. On October 7, 1571, the Holy League defeated the Ottoman fleet at Lepanto. Tradition holds that the pope, in Rome, suddenly broke off a meeting at the moment of victory and walked to a window: 'It is not the time for business; let us go and thank God for the victory He has just given to the Christian arms.'
He instituted the feast of Our Lady of Victory in thanksgiving; his successor Gregory XIII renamed it the feast of the Most Holy Rosary, still kept on October 7. Pius V died in 1572 of bladder stones, refusing his physicians' suggestion that they spare him further suffering. He was canonised in 1712 — the first pope canonised since Pius V's own day made it harder.