James Hamilton, 1st Duke of Abercorn, KG, PC (21 January 1811 – 31 October 1885), styled Viscount Hamilton from 1814 to 1818 and the Marquess of Abercorn from 1818 to 1868, was a British Conservative politician and statesman who twice served as Lord Lieutenant of Ireland.
Born at Seymour Place, Mayfair, Abercorn was the son of James Hamilton, Viscount Hamilton, himself the eldest son of John Hamilton, 1st Marquess of Abercorn. His mother, Harriet, was the second daughter of the Hon. John Douglas, himself the son of James Douglas, 14th Earl of Morton. His father died when Abercorn was only three. In 1818, aged seven, he succeeded his grandfather in his titles and estates. He was educated at Harrow School and Christ Church, Oxford. In 1856, he received an Honorary Doctorate of Civil Laws from the University of Oxford.
On 12 December 1844, Lord Abercorn was made a Knight of the Garter at the relatively young age of 33, becoming on 13 November of same year Lord Lieutenant of Donegal and Deputy Lieutenant of Tyrone. On 25 February 1846 he was appointed a Privy Counsellor and Groom of the Stole to Prince Albert, and remained a prominent figure in the royal court for the next two decades. In 1866, he was appointed Viceroy of Ireland, and two years later was created Marquess of Hamilton (in the Peerage of the United Kingdom) and Duke of Abercorn (in the Peerage of Ireland), resigning shortly after Gladstone won the 1868 general election. He was reappointed to the post in 1874, and the Duke served as Viceroy until his resignation in 1876, partly on account of his wife's ill health. In 1874, he was chosen Grand Master of the Grand Lodge of Ireland, a post he held until his death. Abercorn was Envoy-Extraordinary for the investiture of King Umberto I of Italy with the Order of the Garter on 2 March 1878. He was elected Chancellor of the University of Ireland in 1881, and died four years later at his home of Baronscourt, County Tyrone.