Helen Selina Blackwood, Baroness Dufferin and Claneboye (née Sheridan, 1807 – 13 June 1867), later Countess of Gifford, was a British songwriter, composer, poet, and author. Admired for her wit and literary talents, she was a well-known figure in London society of the mid-19th century.
Helen Sheridan came from a literary and theatrical family with political connections. Her father, Thomas Sheridan (1775–1817), an actor, soldier and colonial administrator, was the younger son of famous Irish playwright Richard Brinsley Sheridan, and her mother was Caroline Henrietta Sheridan (née Callander), a novelist. In 1813, Thomas took Helen and his wife with him to a post at the Cape of Good Hope, where he died four years later on 12 September 1817. Helen then returned to England where she lived in a Hampton Court Palace "grace and favour" apartment with her mother, four brothers and two younger sisters. The sisters' beauty and accomplishments led to them being called the "Three Graces". Caroline was known as the wittiest of the girls and later developed into a talented writer, and Georgiana, considered the prettiest of the sisters, later became Duchess of Somerset by marriage to Edward Seymour, 12th Duke of Somerset.
At seventeen, Helen was engaged to Commander Price Blackwood, youngest of three sons of the 3rd Baron Dufferin and Claneboye, and Mehetabel Temple; owing to the deaths of his brothers he was to be the future Lord Dufferin, although his parents wanted him to marry more advantageously, mainly based on financial grounds. After their London wedding at St. George's, Hanover Square, London, on 4 July 1825, they went to live in Florence due to the opposition of the marriage by the Blackwood family, but returned two years later with their baby son Frederick, who was born on 21 June 1826. Her sisters introduced her to fashionable circles where she mixed with prominent figures of the time, Mary Berry, Samuel Rogers, Henry Taylor, Brougham, Sydney Smith, and Benjamin Disraeli; Disraeli in later life said she had been "his chief admiration". In 1839, she became Lady Dufferin when her husband inherited his title. He died in 1841 of an accidental morphine overdose; Helen continued to spend her summers at his family estate at Clandeboye in Ireland, which now belonged to Frederick.