Lady Jane Grey (c. 1537 – 12 February 1554), later known as Lady Jane Dudley (after her marriage) and as the "Nine Days' Queen", was a teenage English noblewoman who claimed the throne of England and Ireland from 10 July until 19 July 1553.

Jane was the great granddaughter of Henry VII through his younger daughter Mary, and was a first cousin once removed of Edward VI. She had an excellent humanist education, and a reputation as one of the most learned young women of her day. In May 1553, she married Lord Guildford Dudley, a younger son of Edward's chief minister John Dudley, Duke of Northumberland. In June 1553, Edward VI wrote his will, nominating Jane and her male heirs as successors to the Crown, in part because his half-sister Mary was Catholic, while Jane was a committed Protestant and would support the reformed Church of England, whose foundation Edward laid. The will removed his half-sisters, Mary and Elizabeth, from the line of succession on account of their illegitimacy, subverting their claims under the Third Succession Act.

After Edward's death, Jane was proclaimed queen on 10 July 1553, and awaited coronation in the Tower of London. Support for Mary grew quickly, and most of Jane's supporters abandoned her. The Privy Council of England suddenly changed sides, and proclaimed Mary as queen on 19 July 1553, deposing Jane. Her primary supporter, her father-in-law, the Duke of Northumberland, was accused of treason, and executed less than a month later. Jane was held prisoner in the Tower, and was convicted of high treason in November 1553, which carried a sentence of death.

Mary initially spared her life; however, Jane soon became viewed as a threat to the Crown when her father, Henry Grey, 1st Duke of Suffolk, became involved with Wyatt's rebellion against Queen Mary's intention to marry Philip II of Spain. Jane and her husband were executed on 12 February 1554.