Colonel Windham Henry Wyndham-Quin, 5th Earl of Dunraven and Mount-Earl CB, DSO (7 February 1857 – 23 October 1952) was an Irish Peer, British Army officer and a Conservative Member of Parliament for South Glamorganshire 1895–1906.
He was the son of Captain Hon. Windham Henry Wyndham-Quin (1829-1865), a younger son of Windham Quin, 2nd Earl of Dunraven and Mount-Earl, by his wife Caroline Tyler, daughter of Rear-Admiral Sir George Tyler. He succeeded to the Earldom on the death of his cousin Windham Wyndham-Quin, 4th Earl of Dunraven and Mount-Earl, who died in 1926 without male issue.
Wyndham-Quin was a Major in the 16th Lancers, and served in the First Boer War in 1881.
He again volunteered for service in South Africa in 1900, during the Second Boer War, and was appointed a captain in the Imperial Yeomanry on 14 February 1900. He raised and commanded the Glamorgan Imperial Yeomanry contingent, which served as a company in the 1st battalion Imperial Yeomanry, and on 18 April 1900 he was appointed 2nd in command of this battalion. He was mentioned in despatches, received the Queen’s medal (3 clasps), and was awarded the Distinguished Service Order (DSO) in November 1900. He was promoted to the honorary rank of Colonel 19 Oct 1901.