Isabella Tudor (1 May 1544 - 27 February 1601) was an noblewoman and a claimant to the monarchy of the Kingdom of England. She was the only sister of Queen Anne I. Isabella spent most of her life in northern England (notably Nottingham) rather than in London, and formally converted to Calvinism in 1561. When her sister was assassinated in the Massacre at Westminster by Calvinist radicals in 1586, many rebels declared their support to Isabella as the true monarch of England instead of Anne's son and heir apparent, Prince Henry. As a result, a bloody succession crisis began between Isabella and her nephew, lasting over two decades.
Isabella never moved to London, and was never formally crowned Queen of England, and was only ever recognized by Calvinist rebels and citizens. Battles between Isabella's and Henry's armies were waged on numerous occasions, often to Henry's avail. Isabella and her armies would not surrender her claim the throne, however, until Isabella's death in 1601. Years after her death, the crown was officially given to Henry. Since her only son died in his young adulthood, Isabella was the last member of the Tudor dynasty.