The English Reformation was the process by which Protestantism emerged in England and surpassed Catholicism as the dominant faith in the country. While Protestant ideas had first penetrated England under John Wycliffe in the late 14th and early 15th centuries, it was not until the reign of King Henry VIII that Protestantism was able to take root in English government and high society. King Henry declared himself the Supreme Head of the Church of England in 1534, splitting with the Catholic Church politically, but not on doctrine. During the English Reformation, the printing press and the translation of the Bible into the vernacular led to the spread of Protestant ideas across southern England; however, only London and the major port cities became Protestant strongholds; Protestantism did not spread into the countrysides of northern England for decades, leading to the Pilgrimage of Grace rebellion and the overthrow of the Protestant royal claimant Lady Jane Grey by Queen Mary I of England's Catholic supporters after a nine-day reign in 1553. The Catholic Church was dismantled through the 1534 Act of Supremacy and the Dissolution of the Monasteries under King Henry VIII, and, during the reign of Henry VIII's son Edward VI of England from 1547 to 1553, the theology and liturgy of the Church of England became markedly Protestant due to the adoption of the Book of Common Prayer and the influence of the Archbishop of Canterbury Thomas Cranmer.
Under the Catholic Mary I, who seized power in 1553, the Church of England was reconciled with Rome, and her new Archbishop of Canterbury Reginald Pole became the first and last Cardinal in England from Thomas Wolsey's death until the Catholic emancipation of the 19th century. While Protestant reformers had been persecuted during the reign of the doctrinally-Catholic Henry VIII, Queen Mary and her advisor Stephen Gardiner stepped up the persecution of all Protestants in the country (including the execution of Cranmer), earning Mary the derisive nickname "Bloody Mary." Mary's plan to marry Prince Philip of Spain, a staunch Catholic, provoked Wyatt's Rebellion, a failed Protestant uprising which was crushed by Mary's loyalists; Mary responded by having Lady Jane Grey, Lord Guildford Dudley, and several other Protestant leaders executed, while she also imprisoned her own sister, Princess Elizabeth, another staunch Protestant, in the Tower of London. Queen Mary's death in 1559 led to Elizabeth becoming the new Queen of England, and she re-established royal supremacy over the Church of England as "Supreme Governor" and once again made England a Protestant country.
The Anglican church was not the only Protestant denomination to wield influence in England, however. Calvinist dissenters seeking to reform or leave the church split from the Church of England, and Presbyterian ideas penetrated northern England from Scotland due to the charismatic teachings of John Knox. The reformist dissenters sought to remove Catholic influences from the church (to "purify" it; hence "Puritanism"), while others (the "Separatists") sought to leave the church and establish a more "authentic" form of Protestantism. By the 17th century, Presbyterianism, Congregationalism, and other denominations had emerged, protesting against the "Catholicization" of the Church of England under the House of Stuart. These dissenters also opposed the supremacy of the English monarchs over the Church of England and over Parliament, and, following the English Civil War of the 1640s, a short-lived Puritan-led English Commonwealth emerged under Oliver Cromwell.
By the time of the civil war, around 15-25% of the English population was still Catholic, with the largest concentrations of Catholicism being in the northern and western parts of England, particularly in Lancashire, Yorkshire, and parts of the Midlands. In Cornwall alone, around 50-60% of the Cornish population remained Catholic, with the region's remote, rugged geography helping the Catholic faith persist there longer than in many other regions. Other pockets of Catholicism were found in the areas around the great Catholic noble families, such as the Howards in Norfolk and the Talbots in Shropshire. Cities like London, Oxford, and Bristol also had substantial Catholic minorities. During the war, the Parliamentarian army was roughly 60-70% Puritan and Presbyterian, the other 30-40% being mostly Anglican. London and the surrounding Home Counties were predominantly Puritan and Presbyterian, East Anglia was a stronghold of Puritanism, the Midlands were mixed with Puritan, Anglican, and Catholic influences, Northern England had significant pockets of Catholicism as well as Anglicanism and Puritanism, the West Country had a relatively high proportion of Anglicans and Catholics, and Cornwall was mostly Catholic, with some Anglican presence.
In 1688, the last Catholic monarch of England, James II of England, was deposed by the Dutch Protestant William of Orange, marking the end of Catholic rule in England. William reinforced the Church of England's supremacy in the country, and it was not until 1829 that Catholics were allowed to openly practice their faith in the United Kingdom.