Bou Ismaïl (Algerian Arabic: بو إسماعيل) is a city in Bou Ismaïl District, Tipasa Province, Algeria. In 1998 it had a population of 27,000. Its French colonial name was Castiglione.
Coordinates: 36°39′N 2°42′E / 36.650°N 2.700°E / 36.650; 2.700