Stewart of Darnley was a notable Scots family, a branch of the Clan Stewart, who provided the English Stuart monarchs with their male-line Stuart descent, after the reunion of their branch with the royal Scottish branch, which led to the ultimate union of the two main kingdoms of Great Britain: England and Scotland.
In 1565 the House of Stewart of Darnley was re-united with the Royal House of Stewart when Henry Stuart, Lord Darnley married his first cousin, Mary, Queen of Scots, both being grandchildren of Margaret Tudor, daughter of King Henry VII of England, and hence both having claim to the English throne. The son of this union James VI of Scots succeeded to the throne of England as James I.
The later English Kings of the House of Stuart, from James I and Charles I onwards, were more properly members of the Stewart of Darnley branch, and all drew upon their feudal heritage in Lennox.
The Stewarts of Darnley were descended from Sir John Stewart of Bonkyll, the second son of Alexander Stewart, 4th High Steward of Scotland . Their name is derived from Derneley, a barony in Eastwood parish, Renfrewshire one & a half miles east of Barrhead, present day Darnley, within the city of Glasgow. In 1356, Robert Stewart, High Steward of Scotland granted the barony to Sir John Stewart.