Earl of Sunderland is a title that has been created twice in the Peerage of England. The first creation came in 1627 in favour of Emanuel Scrope, 11th Baron Scrope of Bolton. The earldom became extinct upon his death in 1630, while the barony became either extinct or dormant (see Baron Scrope of Bolton for more information on this title). The second creation came in 1643 in favour of the Royalist soldier Henry Spencer, 3rd Baron Spencer of Wormleighton.
The Spencer family descended from Sir John Spencer (d. 1522), who acquired the Wormleighton estate in Warwickshire and the Althorp estate in Northamptonshire. His grandson Sir John Spencer (d. 1586) was a Knight of the Shire for Northamptonshire. The latter's grandson Sir Robert Spencer represented Brackley in Parliament during the late 16th century. In 1603, Sir Robert was raised to the Peerage of England as Baron Spencer of Wormleighton. He was succeeded by his eldest surviving son, William, the second Baron. He had previously represented Northamptonshire in Parliament. His eldest son was the aforementioned third Baron. In July 1643, he was created Earl of Sunderland in the Peerage of England, but he was killed at the Battle of Newbury in September of the same year. He was succeeded by his two-year-old only son, Robert, the second Earl. He later gained great distinction as a statesman and notably served four times as Secretary of State for the Southern Department.
His eldest surviving son, Charles, the third Earl, also gained prominence as a statesman. He was Lord-Lieutenant of Ireland, Lord Privy Seal, Secretary of State for both the Northern and Southern Departments, Lord President of the Council and First Lord of the Treasury. However, his political career was ruined by the South Sea Bubble of 1720. Lord Sunderland married (as his second wife) Lady Anne Churchill, second daughter of the distinguished soldier John Churchill, 1st Duke of Marlborough, and Sarah Jennings. The dukedom of Marlborough was allowed to descend to the Duke's daughters and their sons after a special Act of Parliament was passed in 1716.
The third Earl was succeeded by his eldest surviving son (by his second wife), Robert, the fourth Earl. He died unmarried in 1729 at the age of 27 and was succeeded by his younger brother, Charles, the fifth Earl. In 1733, he succeeded his maternal aunt, Henrietta Godolphin, 2nd Duchess of Marlborough, as third Duke of Marlborough. The barony of Spencer of Wormleighton and earldom of Sunderland have remained subsidiary titles of the dukedom ever since. Earl of Sunderland has been used as the courtesy title of the Duke's eldest male-line grandson.
John Spencer, fourth son of the third Earl of Sunderland by his second wife, succeeded to the family estates in Northamptonshire in 1733 after his elder brother inherited the dukedom of Marlborough. His son John was created Earl Spencer in 1765. Robert Spencer, second son of the second Baron, had been created Viscount Teviot in 1685.
For further succession, see Duke of Marlborough (title).