The title Earl Cowley was created in the Peerage of the United Kingdom in 1857 for Lord Cowley, the longtime British ambassador in Paris. The 1st Earl's father, Henry Wellesley, 1st Baron Cowley, was a younger brother of the 1st Duke of Wellington.

The Earl bears the subsidiary titles of Viscount Dangan, of Dangan in the County of Meath (1857), and Baron Cowley, of Wellesley in the County of Somerset (1828), both in the Peerage of the UK.

Barons Cowley (1828)

• Henry Wellesley, 1st Baron Cowley (1773-1847)
• Henry Richard Charles Wellesley, 2nd Baron Cowley (1804-1884) (created Earl Cowley in 1857)

Earls Cowley (1857)

• Henry Richard Charles Wellesley, 1st Earl Cowley (1804-1884)
• William Henry Wellesley, 2nd Earl Cowley (1834-1895)
• Henry Arthur Mornington Wellesley, 3rd Earl Cowley (1866-1919)
• Christian Arthur Wellesley, 4th Earl Cowley (1890-1962)
• Denis Arthur Wellesley, 5th Earl Cowley (1921-1968)
• Richard Francis Wellesley, 6th Earl Cowley (1946-1975)
• Garret Graham Wellesley, 7th Earl Cowley (b. 1934)

Heir Apparent: Garret Graham Wellesley, Viscount Dangan