Mary I (18 February 1516 – 17 November 1558), also known as Mary Tudor, was Queen of England and Queen of Ireland from 6 July 1553 (de jure) or 19 July 1553 (de facto) until her death in 1558.

Mary, the fourth and penultimate monarch of the Tudor dynasty, is remembered for her attempt to return England from Protestantism to Roman Catholicism. To this end, she had almost three hundred religious dissenters executed; as a consequence, she is often known as Bloody Mary. Her religious policies, however, were in many cases reversed by her successor and half-sister, Elizabeth I.

Edward VI died in 1553 while Mary was staying at Framlingham Castle in Suffolk. He did not desire that the Crown go to either the Lady Mary or the Lady Elizabeth; consequently, he excluded them from the line of succession in his will, which was unlawful, because it contradicted an act of Parliament passed in 1544 restoring the Lady Mary and the Lady Elizabeth to the line of succession, and because it was made by a minor. Under the guidance of John Dudley, 1st Duke of Northumberland, Edward VI instead devised the Crown to the Lady Jane Grey, a descendant of Henry VIII's younger sister, Mary Tudor, Duchess of Suffolk, and the Duke of Northumberland's daughter-in-law.

Thus, after Edward died on 6 July 1553, the Lady Jane Grey was proclaimed Queen. Jane's accession was met with popular disapproval, which was suppressed by the use of force. A young boy so bold as to hail "Queen Mary" was punished by having his ears cut off. Still, the country remained devoted to Mary.

On July 19, Lady Jane's accession proclamation was deemed to have been made under coercion and was revoked; instead, Mary was proclaimed queen. All support for the Lady Jane vanished and Mary rode into London triumphantly and unchallenged, with her half-sister, the Lady Elizabeth, at her side, on August 3rd.

Since the Act of Succession passed in 1544 recognized only Mary as Edward's heir, and since Edward's will was never authorized by statute, Mary's de jure reign dates to July 6 1553, the date of Edward's death. Her de facto reign, however, dates to July 19, 1553, when Jane was deposed. One of her first actions as monarch was to order the release of the Catholic Thomas Howard, 3rd Duke of Norfolk, and Stephen Gardiner from imprisonment in the Tower of London.

Originally, Mary was inclined to exercise clemency. She set the Lady Jane Grey free, recognizing that the young girl was forced to take the crown by her father-in-law. The Lady Jane's father, Henry Grey, 1st Duke of Suffolk, was also released. The Duke of Northumberland was the only conspirator immediately executed for high treason, and even this was after some hesitation on the Queen's part.

She was left in a difficult position, as almost all the Privy Counsellors had been implicated in the plot to put the Lady Jane Grey on the throne. She could only rely on Stephen Gardiner, whom she appointed Bishop of Winchester and Lord Chancellor. Gardiner performed Mary's coronation on October 1, 1553 because Mary did not wish to be crowned by the senior ecclesiastics, who were all Protestants.

Mary's first act of Parliament retroactively validated Henry VIII's marriage to Catherine of Aragon, and legitimated the queen.

Now 37, Mary turned her attention to procuring a husband to father an heir in order to prevent her half-sister, the Lady Elizabeth, from succeeding to the Throne. She rejected Edward Courtenay, 1st Earl of Devon as a prospect when her first cousin, the Holy Roman Emperor Charles V, suggested that she marry his only son, the Spanish Prince Philip.

The marriage, a purely political alliance for Philip, was extremely unpopular with the English. Lord Chancellor Gardiner and the House of Commons petitioned her to consider marrying an Englishman, fearing that England would be relegated to a dependency of Spain. Insurrections broke out across the country when she refused. The Duke of Suffolk once again proclaimed that his daughter, the Lady Jane Grey, was Queen.

The young Sir Thomas Wyatt led a force from Kent, and was not defeated until he had arrived at London's gates. After the rebellions were crushed, both the Duke of Suffolk and the Lady Jane Grey were convicted of high treason and executed. Since the rebellion was designed to put her on the throne, the Lady Elizabeth was imprisoned in the Tower of London, but was put under house arrest in Woodstock Palace after two months.

Mary married Philip on July 25, 1554 at Winchester Cathedral. Under the terms of the marriage treaty, Philip was to be styled "King of England," all official documents (including acts of Parliament) were to be dated with both their names and Parliament was to be called under the joint authority of the couple. Philip's powers, however, were extremely limited; he and Mary were not true joint sovereigns.

Nonetheless, Philip was the only man to take the crown matrimonial upon his marriage to a reigning queen of England; William III became jointly sovereign with his wife, Mary II, pursuant to act of Parliament, rather than matrimonial right. Coins were to also show the head of both Mary and Philip.

The marriage treaty further provided that England would not be obliged to provide military support to Philip's father, the Holy Roman Emperor, in any war. Mary fell in love with Philip and, thinking she was pregnant, had thanksgiving services at the diocese of London in November 1554. But Philip found his queen, who was eleven years his senior, to be physically unattractive and after only fourteen months left for Spain under a false excuse. Mary suffered a phantom pregnancy; Philip released the Lady Elizabeth from house arrest so that he could be viewed favourably by her in case Mary died during childbirth.

Mary then turned her attention to religious issues. She had always rejected the break with Rome instituted by her father. Her half-brother, Edward, had established Protestantism; Mary wished to revert to Roman Catholicism. England was reconciled with Rome, and Reginald Cardinal Pole, who would become an adviser Mary very heavily depended upon, became Archbishop of Canterbury. Edward's religious laws were abolished by Mary's first Parliament and numerous Protestant leaders were executed in the so-called Marian Persecutions.

The first to die was John Rogers (February 4, 1555) and the next to be killed was John Hooper, the Bishop of Gloucester (February 9, 1555). The persecution lasted uninterrupted for three and three-quarter years. She earned the epithet of Bloody Mary even though her successor and half-sister, Elizabeth, more than balanced the number killed under Mary with Catholic persecution, in total, but not in frequency. (Elizabeth reigned seven times as long, and some of her executions were of actual traitors, under any definition.)

Having inherited the throne of Spain upon his father's abdication, Philip returned to England from March to July 1557 to persuade Mary to join with Spain in a war against France in the Italian Wars. Meanwhile, England was full of faction, and seditious pamphlets of Protestant origin inflamed the people with hatred against the Spaniards. But perhaps the strangest thing about the situation was that the Pope sided with France against Spain. English forces fared badly in the conflict and as a result the kingdom lost Calais, its last remaining continental possession. Mary later lamented that when she lay dead the words "Philip" and "Calais" would be found inscribed on her heart.

Mary also set in motion currency reform to counteract the dramatic devaluation of the currency overseen by Thomas Gresham that characterized the last few years of Henry VIII's reign and the reign of Edward VI. These measures, however, were largely unsuccessful and it was only under Elizabeth that economic catastrophe was prevented. Mary's deep religious convictions also inspired her to institute social reforms, although these were unsuccessful as well.

Under her reign, in another of the Plantations of Ireland, English colonists were settled in the Irish midlands to reduce the attacks on the Pale (the colony around Dublin). Two counties were created and, in her honour, were named Queens County and, for Phillip, Kings County. The county town of Queens County was called Maryborough.