Mary I (18 February 1516 – 17 November 1558) was the Queen of England and Ireland from July 1553 until her death. Her executions of Protestants caused her opponents to give her the sobriquet "Bloody Mary".

She was the only child of Henry VIII and his first wife Catherine of Aragon who survived to adulthood. Her younger half-brother Edward VI (son of Henry and Jane Seymour) succeeded their father in 1547. When Edward became mortally ill in 1553, he attempted to remove Mary from the line of succession because of religious differences. On his death their first cousin once removed, Lady Jane Grey, was initially proclaimed queen. Mary assembled a force in East Anglia and successfully deposed Jane, who was ultimately beheaded. Mary was—excluding the disputed reigns of Jane and the Empress Matilda—the first queen regnant of England. In 1554, Mary married Philip of Spain, becoming queen consort of Habsburg Spain on his accession in 1556.

As the fourth crowned monarch of the Tudor dynasty, Mary is remembered for her restoration of Roman Catholicism after the short-lived Protestant reign of her half-brother. During her five-year reign, she had over 280 religious dissenters burned at the stake in the Marian persecutions. Her re-establishment of Roman Catholicism was reversed after her death in 1558 by her younger half-sister and successor Elizabeth I, daughter of Henry and Anne Boleyn.