James Hamilton, 1st Duke of Abercorn (January 21, 1811) - (October 31, 1885) was a British Conservative nobleman and politician who twice served as Lord Lieutenant of Ireland.

His full title was: The Most Noble Sir James Hamilton, 1st Duke of Abercorn, Marquess of Abercorn, Marquess of Hamilton, Earl of Abercorn, Viscount Strabane, Viscount Hamilton, Lord Paisley, Lord Hamilton, Mountcastle and Kilpatrick, Baron Hamilton of Strabane, Baron Mountcastle, Knight of the Most Noble Order of the Garter, Her Majesty's Most Honourable Privy Counsellor.

Born in Mayfair, London, the son of James Hamilton, Viscount Hamilton, who died when he was only three, he 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, by whom he had numerous children.

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 Lord Lieutenant of Ireland, and two years later was created Duke of Abercorn and Marquess of Hamilton, resigning shortly afterwards after Gladstone won the General Election. Reappointment to the post came in 1874, and the Duke was for a second time Lord Lieutenant until his resignation in 1876, partly on account of his wife's ill health. He was later elected Chancellor of the University of Ireland in 1881, and died four years later at his home of Baronscourt, County Tyrone.

His children included James Hamilton, 2nd Duke of Abercorn, who succeeded him in the dukedom and who was involved in promoting British imperialism in Africa; Lord George Hamilton, a Conservative politician who served in the cabinets of Lord Salisbury; and numerous daughters all of whom married gentlemen of the rank of Earl or higher: Harriet married the Earl of Lichfield, Beatrix the Earl of Durham, Louisa the Duke of Buccleuch, Katherine the Earl of Mount Edgcumbe, Georgiana the Earl Winterton, Alberta the Duke of Marlborough, and Maud the Marquess of Lansdowne.