Pope Pius V was the 225th pope of the Roman Catholic Church, serving from 1566 to 1572. He is best known for excommunicating Queen Elizabeth I of England and for implementing the reforms established by the Council of Trent. His papacy focused on the Counter-Reformation, aiming to address issues within the Church and combat the spread of Protestantism. Pope Pius V is also recognized for the formalization of the Tridentine Mass, which became the standard form of the Roman Catholic liturgy for centuries. He canonized several saints and promoted the use of the rosary, emphasizing the importance of prayer and devotion in the Catholic faith.