Mary I (18 February 1516 – 17 November 1558) was Queen of England and Queen of Ireland from 6 July 1553 (de jure) or 19 July 1553 (de facto) until her death. 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 sometimes known as Bloody Mary. Her religious policies, however, were in many cases reversed by her successor, Elizabeth I.
Mary I is sometimes confused with her cousin, Mary I, Queen of Scots, who lived at approximately the same time.