Rear-Admiral Donat Henchy O'Brien (March 1785 – 13 May 1857) was an officer of the Royal Navy. He was the son of a Royal Navy captain who claimed descent from an ancient Irish king. O'Brien served as a midshipman during the French Revolutionary Wars and commanded a troop-carrying vessel during the Anglo-Russian invasion of Holland. He was afterwards appointed acting lieutenant and served as a master's mate on the frigate . While returning to England in 1804, the ship was wrecked on the Île de Sein and O'Brien and other crew were captured by the French. O'Brien was imprisoned in France but escaped in 1808 and reached a British vessel at Trieste. He later wrote a book about his experiences.