James Hamilton, 1st Duke of Abercorn, KG, PC (January 21, 1811 – October 31, 1885) was a British Conservative nobleman and statesman who twice served as Lord Lieutenant of Ireland. He had various styles during his lifetime, namely The Hon. James Hamilton (until 1814, by virtue of his father's courtesy viscountcy), Viscount Hamilton (1814–1818, while heir to the Marquessate of Abercorn), The Marquess of Abercorn (inherited in 1818), and finally The Duke of Abercorn (so created in 1868).
Born in Mayfair, London, Hamilton was the son of James Hamilton, Viscount Hamilton, who died when his son was only three. Hamilton was educated at Harrow and Christ Church, Oxford. In 1818 he succeeded his grandfather as second Marquess of Abercorn, and in 1832 married Lady Louisa Russell, daughter of John Russell, 6th Duke of Bedford.
In 1844, Lord Abercorn was made a Knight of the Garter at the relatively young age of 33, becoming that same year Lord Lieutenant of County Donegal. Two years later 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 Duke of Abercorn and Marquess of Hamilton, 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. He was also Grand Master of the Freemasons (Ireland) from 1874 until his death. On 2 March, 1878, Abercorn was Envoy-Extraordinary for the investiture of King Umberto I of Italy with the Order of the Garter. He was elected Chancellor of the University of Ireland in 1881, and died four years later at his home of Baronscourt, County Tyrone.