Lionel Seymour William Dawson-Damer, 4th Earl of Portarlington DL (7 April 1832 – 17 December 1892), known as Lionel Dawson-Damer until 1889, was a British peer and Conservative politician.

[2] His father was a younger son of John Dawson, 1st Earl of Portarlington and Lady Caroline Stuart (a daughter of Prime Minister John Stuart, 3rd Earl of Bute).

[3] His maternal grandparents were Lord Hugh Seymour (a younger son of the 1st Marquess of Hertford) and the former Lady Anne Horatia Waldegrave (a daughter of the 2nd Earl Waldegrave).

[4] According to a private letter between Louisa and Eddy Eliot, dated 27 September 1841, their brother's friend "Seymour Damer is gone to school in Liverpool".

Together, they were the parents of several children, including:[4] He died on 17 December 1892, aged 60, and was succeeded in the earldom by his eldest son, Lionel George.