Charles O'Brien, titular 7th Viscount Clare and 9th Earl of Thomond (1757-1774) was a Franco-Irish nobleman.
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He was born on 18 October 1757 in Paris, France, the son of Charles O'Brien, 6th Viscount Clare, maréchal de Thomond and Marie Genevieve Louise Gauthier de Chifreville. He was Colonel-proprietor of the Clare Regiment after his father, but died before assuming effective command. O'Brien died unmarried at 17 of natural causes on 29 December 1774 in Paris.