Admiral Edwin Clayton Tennyson d'Eyncourt CB RN (4 July 1813 – 14 January 1903) was a distinguished British naval officer.
Edwin was the second son of Charles Tennyson d'Eyncourt and Frances Mary Hutton, the only child and heiress of the Rev. John Hutton, Rector of Lea. His paternal grandparents were Elizabeth (née Clayton) Tennyson and George Tennyson. Upon his grandfather's death in July 1835, his father inherited the family estates and changed his family's surname to Tennyson d'Eyncourt. Through his younger brother Louis, he was uncle to Sir Eustace Tennyson d'Eyncourt, 1st Baronet, a naval architect who was the Navy's Director of Naval Construction.
He was a first cousin of the poet Alfred, Lord Tennyson. As a young man, he thoroughly embodied his family's social pretensions and their snobbish behaviour towards their poor relations, the Tennysons of Somersby; but in later years the mutual dislike between him and his famous cousin thawed, and he gave Alfred advice on the law of propriety of accepting the peerage offered to him in 1883.
Tennyson entered naval college in 1826 and became a lieutenant in 1837. He served in the South American, East Indies and China Stations during the 1840s. In 1854, he served in the Baltic campaign under Sir Charles Napier as captain of the gunboat HMS Desperate, and returned to that theatre in 1855 under Rear-Admiral Richard Saunders Dundas, as captain of the steam frigate HMS Pylades. From 1859 to 1862, he was captain of the blockship HMS Edinburgh as the guardship at Leith.
He attained the rank of rear-admiral in 1866 and retired in 1870, continuing to rise to the rank of admiral by 1878. He was made a Companion of the Bath in 1873. After the death of his elder brother George in 1871, he inherited the family estate known as Bayons Manor. In London, they lived in the Pimlico district at 56 Warwick Square.