Final answer:
Henry VIII declared himself the Supreme Head of the Church of England in 1534 with the Act of Supremacy, breaking ties with the Roman Catholic Church and starting the English Reformation.
Step-by-step explanation:
Henry VIII and the Church of England
The monarch who declared himself the Supreme Head of the Church of England and made a definitive break with the pope in Rome was Henry VIII. Henry's quest for a male heir and desire to annul his marriage to Catherine of Aragon were catalysts for this significant religious and political shift. When the Pope refused to annul his marriage, Henry took drastic action that led to the English Reformation. In 1534, the English Parliament enacted the Act of Supremacy, which recognized Henry VIII as the Supreme Head of the Church of England, officially severing ties with the Roman Catholic Church. The Anglican Church, while doctrinally similar to Catholicism, asserted national sovereignty in ecclesiastical matters and became enmeshed in the power structure of the English monarchy.