Thomas Stanley, 1st Earl of Derby, KG (1435 – 29 July 1504) is titular King of Mann, an English nobleman and stepfather to King Henry VII of England.

He is the eldest son of Thomas Stanley, 1st Baron Stanley, and Joan Goushill.

Through his mother he is a lineal descendant of King Edward I by Elizabeth of Rhuddlan, Countess of Hereford and by the FitzAlan family, Stanley is a descendant of King Henry III.

A landed magnate of immense power, particularly across the northwest of England where his authority goes almost unchallenged, even by the Crown, Stanley manages to remain in favor with successive kings throughout the Wars of the Roses until his death in 1504.

His estates include what is now Tatton Park in Cheshire, Lathom House in Lancashire, and Derby House in the City of London, now the site of the College of Arms.

Although the king for the early part of his career, Henry VI, is head of the House of Lancaster, Stanley’s marriage to Eleanor, daughter of Richard Neville, 5th Earl of Salisbury (a descendant of Edward III) and sister of Richard Neville, Earl of Warwick (‘Warwick the Kingmaker’) in the late 1450s constitutes a powerful alliance with the House of York.

This does him no harm, however, even after Warwick is toppled from power, and in 1472, with the House of York now occupying the English throne, he marries his second wife Lady Margaret Beaufort, whose son, Henry Tudor, is the leading Lancastrian claimant.

He is the last to use the style ‘King of Mann’, his successors opting for the safer ‘Lord of Mann’.