Which document marked the official break of the Church of England from the Catholic Church?

The Act of Supremacy is significant because it formally established the Church of England's separation from the authority of the Roman Catholic Church. Enacted in 1534, this document declared that the King of England, specifically Henry VIII at that time, was the Supreme Head of the Church of England. This move was largely motivated by Henry VIII's desire to annul his marriage to Catherine of Aragon, which the Pope refused to grant. The Act of Supremacy thus not only marked a religious transformation but also signified the consolidation of political power under the monarchy, as it severed ties with the papal authority in Rome.

The other documents mentioned do not relate to this specific event. The Magna Carta is a foundational constitutional document from 1215 that limited the powers of the king and laid the groundwork for future governance, while the Apostolic Constitution is associated with the governance of the Catholic Church itself. The Treaty of Westphalia, concluding the Thirty Years' War in 1648, involved issues of state sovereignty and religious tolerance, but was not directly linked to the establishment of the Church of England as separate from Rome.