Final answer:
Henry VIII's conflict with the Catholic Church began over his request to annul his marriage to Catherine of Aragon, which was denied by the Pope, leading to the creation of the Church of England and the start of the English Reformation.
Step-by-step explanation:
Henry VIII first conflicted with the Roman Catholic Church over the annulment of his marriage to Catherine of Aragon. This conflict arose because Henry needed a male heir to continue the Tudor dynasty, but Catherine was unable to provide one. When the Pope denied his request for an annulment on various grounds, including political pressure and the potential theological implications of declaring a papal dispensation invalid, Henry established the Church of England and declared the English church independent of Rome's authority. As a result, Parliament passed the Act of Supremacy in 1534, which established the king as the supreme head of the Church of England, effectively starting the English Reformation.