Earl of Harrington is a title in the Peerage of Great Britain that was created in 1742.

The earldom of Harrington was granted in 1742 to William Stanhope, 1st Baron Harrington, the former Secretary of State and then Lord President of the Council. He was made Viscount Petersham at the same time.^[1] In 1730, he had been created Baron Harrington, of Harrington in the County of Northampton. These titles were also in the Peerage of Great Britain. Lord Harrington was the son of John Stanhope of Elvaston and the great-grandson of Sir John Stanhope of Elvaston, younger half-brother of Philip Stanhope, 1st Earl of Chesterfield (who was the grandfather of James Stanhope, 1st Earl Stanhope).^[1]

Lord Harrington was succeeded by his son, the second Earl.^[2] He was a General in the Army and also represented Bury St Edmunds in the House of Commons. His son, the third Earl, was also a General in the Army and sat as Member of Parliament for Thetford and Westminster. His elder son, the fourth Earl, and younger son, the fifth Earl, were both Colonels in the Army.

The line of the fifth Earl failed in 1866 upon the early death of his son, the sixth Earl. The latter was succeeded by his first cousin, the seventh Earl. He was the son of the Very Reverend and Hon. FitzRoy Henry Richard, fourth son of the third Earl.^[1] His elder son, the eighth Earl, was a successful polo player. He was succeeded by his younger brother, the ninth Earl.^[3] His grandson, the eleventh Earl, succeeded his father in 1929.

In 1967, the eleventh Earl also succeeded as eighth Viscount Stanhope (of Mahon) and eighth Baron Stanhope (of Elvaston) upon the death of his distant relative James Stanhope, 7th Earl Stanhope, by a special remainder in these titles' patent that allowed them to be inherited by the male heirs of the aforementioned John Stanhope, father of the first Earl of Harrington. As of 2016^[update], the titles are held by the eleventh Earl's son, the twelfth Earl, who succeeded his father in 2009.

The family seat now is The Glen, near Ballingarry, County Limerick. The former family seat was Elvaston Castle, in Derbyshire. The house and grounds are currently owned by Derbyshire County Council, which has opened the gardens as a country park. The 5th Earl had a London townhouse built on land formerly belonging to Kensington Palace – Harrington House remained in the family until the First World War. It is currently home to the Russian Embassy.

Serena Armstrong-Jones, Countess of Snowdon, wife of the 2nd Earl of Snowdon, nephew of Queen Elizabeth II and a member of the extended British royal family, is the daughter of the 12th Earl of Harrington.

• William Stanhope, 1st Baron Harrington (1683–1756) (created Earl of Harrington in 1742)

• William Stanhope, 1st Earl of Harrington
• Elvaston Castle in 1992
• Elvaston Castle in 2005
• Arms of Stanhope, Earls of Harrington (with a crescent or for difference), displayed on the gates of Elvaston Castle

• Earl of Chesterfield
• Earl Stanhope
• Baron Stanhope