||This article relies largely or entirely upon a single source. (October 2014)
Count Patrick D'Arcy ( 27 September 1725 – 18 October 1779 ) was an Irish mathematician and soldier.
Born at Kiltullagh House, County Galway, D'Arcy was a descendant of the Irish Confederate Patrick D'Arcy (1598–1668), his parents were John D'Arcy and Jane (née Lynch; a daughter of Sir Robert Blosse Lynch), both members of the Tribes of Galway.
At age fourteen he was sent to France under the care of an uncle, Martin D'Arcy, a banker in Paris. He studied mathematics under Clairaut, and resided in his house for some time. He joined the French Army, being Colonel in the Irish Brigade at the Battle of Rossbach in 1757. He married his cousin Jane D'Arcy, who became a lady-in-waiting to Marie Antoinette.
In 1749, D'Arcy was elected a member of the French Academy of Sciences, and had the title of Count conferred upon him. He died in Paris in 1779, aged 54, and was buried in the Church of Saint-Philippe du Roule.
- Count Patrick D'Arcy: An eminent Galwayman of the 18th Century, M. Redington, J.G.A.H.S., 10, pp. 58–66.