The Act of Supremacy established the reigning monarch of England as the head of the Church of England, thereby removing ecclesiastical authority over England from the Catholic pope. The Act of Supremacy refers to two separate acts passed in 1534 and 1559 by the English Parliament. After the death of King Henry VIII, the Act of Supremacy was repealed by Queen Mary I before being reinstated by Queen Elizabeth I.
The original Act of Supremacy in 1534 was pushed by King Henry VIII of the Tudor dynasty with the aim of giving him the authority to legalize his divorce from Katherine of Aragon. The divorce had previously been denied by the Catholic Papacy. The Act of Supremacy also gave Henry the ability to seize assets from existing Church monasteries.
With the Act of Supremacy, the Church of England became the de facto religious authority in the Kingdom of England. This allowed Henry VIII to subsidize his precarious financial status through assets seized from the Church. The Act also made supporting the Catholic Pope over the Church of England an act of treason, making it a crime punishable by death.
The Act of Supremacy passed by Queen Elizabeth I in 1559 incorporated an Oath of Supremacy which required individuals taking church or public office to swear their allegiance to the monarch as head of the state and church.