English Parliament passes the first Act of Supremacy, making King Henry VIII head of the Anglican Church, supplanting the pope and the Roman Catholic Church.

The Acts of Supremacy are two acts passed by the Parliament of England in the 16th century that established the English monarchs as the head of the Church of England; two similar laws were passed by the Parliament of Ireland establishing the English monarchs as the head of the Church of Ireland. The 1534 act declared King Henry VIII and his successors as the Supreme Head of the Church, replacing the Pope. This first act was repealed during the reign of the Catholic Queen Mary I. The 1558 act declared Queen Elizabeth I and her successors the Supreme Governor of the Church, a title that the British monarch still holds.

Henry VIII was King of England from 22 April 1509 until his death in 1547. Henry is known for his six marriages and his efforts to have his first marriage annulled. His disagreement with Pope Clement VII about such an annulment led Henry to initiate the English Reformation, separating the Church of England from papal authority. He appointed himself Supreme Head of the Church of England and dissolved convents and monasteries, for which he was excommunicated by the pope.

The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.27 to 1.41 billion baptized Catholics worldwide as of 2025. It is among the world's oldest and largest international institutions and has played a prominent role in the history and development of Western civilization. The Church consists of 24 sui iuris (autonomous) churches, including the Latin Church and 23 Eastern Catholic Churches, which comprise almost 3,500 dioceses and eparchies around the world, each overseen by one or more bishops. The pope, who is the bishop of Rome, is the chief pastor of the church.