St. Pius V was born Michele Ghislieri in 1504 to poor parents of noble lineage at Bosco, near Alexandria, Lombardy on January 17, 1504. He worked as a shepherd until the age of 14 when he encountered two Dominicans who recognized his intelligence and virtue. He joined the Dominicans and was ordained a priest at 24. He taught philosophy and theology for 16 years during which he was elected prior of many houses. He was known for his austere penances, his long hours of prayer and fasting, and the holiness of his speech.

He was elected Bishop of Sutri in 1556, and served as an inquisitor in Milan and Lombardi, and then as inquisitor general of the Church and a cardinal in 1557. He was known in this capacity as an able, yet unflinching man who rigorously fought heresy and corruption wherever he encountered it.

He was elected Pope on January 7, 1566, with the influential backing of his friend St. Charles Borromeo, and took the name Pius V.  He immediately put into action his vast program of reform by getting rid of many of the extravagant luxuries then prevalent in his court. He gave the money usually invested in these luxuries to the poor whom he personally cared for, washing their feet, consoling those near death, and tending to lepers and the very sick. He spent long hours before the Blessed Sacrament despite his heavy workload.

His pontificate was dedicated to applying the reforms of the Council of Trent, raising the standard of morality and reforming the clergy, and strongly supporting foreign missions. The Catechism of the Council of Trent was completed during his reign, and he revised the Roman Breviary and Missal, which remained in use until the reforms of Vatican II.

His six year pontificate saw him constantly at war with two massive enemy forces; the Protestant heretics and the spread of their doctrines in the West, and the Turkish armies who were advancing from the East. He encouraged efforts to battle Protestantism by education and preaching, and giving strong support to the newly formed Society of Jesus, founded by St. Ignatius of Loyola. He excommunicated Queen Elizabeth I, and supported Catholics who were oppressed and intimidated by Protestant princes, especially in Germany.

He worked hard to unite the Christian armies against the Turks, and perhaps the most famous success of his papacy was the miraculous victory of the Christian fleet in the battle of Lepanto on October 7, 1571. The island of Malta was attacked by the Turkish fleet, and nearly every man defending the fortress was killed in battle. The Pope sent out a fleet to meet the enemy, requesting that each man on board pray the Rosary and receive communion. Meanwhile, he called on all of Europe to recite the Rosary and ordered a 40 hour devotion in Rome during which time the battle took place. The Christian fleet, vastly outnumbered by the Turks, inflicted an impossible defeat on the Turkish navy, demolishing the entire fleet.

In memory of the triumph, he declared the day the Feast of Our Lady of the Rosary because of her intercession in answering the mass recitation of the Rosary and obtaining the victory. He has also been called ‘the Pope of the Rosary’ for this reason.

Pope Pius V died seven months later on May 1, 1572, of a painful disease, uttering "O Lord, increase my sufferings and my patience!" He is enshrined at Santa Maria Maggiore in Rome, and was beatified by Clement X in 1672. He was canonized by Clement XI in 1712.