Mostaganem, chief town of an arrondissement in the department of Oran, Algeria, 44 m. E.N.E. of Oran, on a plateau 278 ft. high, half a mile from the Mediterranean coast. The town is separated into European and native quarters by a deep ravine, the Ain Sefra, through which passes a considerable stream. The native quarter, called Tijit, occupies the eastern slopes of the ravine and the level ground above, and is dominated by the kubbas of two marabouts. A railway line, completed in 1889, 122 m. long, connects Mostaganem with Tiaret, the most convenient place for visiting the Jedars monuments. (See Algeria.) Mostaganem occupies the site of a Roman town. The ancient harbour was destroyed by earthquake in the reign of the emperor Gallien. The present port is entirely artificial. The existing town appears to date from the time of the Almoravides, who built the citadel, now turned into a prison. It passed into the possession of the rulers of Tlemcen and was captured by Arouj Barbarossa in 1516, and became part of his brother Khair-ed-Din's kingdom. In the 16th century the town enjoyed a period of great commercial prosperity, and its population rose to 40,000. The re-awakening of the town dates from the French occupation in 1833. Pop. (1906) of the town, 19,528, of the commune 22,011, of the arrondissement, comprising 27 communes, 332,684.
In the vicinity of - Mostaganem are the Dahra mountains, honeycombed with caves. In 1845, in one of these caves, a French force, commanded by Colonel Pelissier, afterwards commander-in-chief of the French army in the Crimea, destroyed over 800 Arabs - men, women and children - by suffocation, by filling the mouths of the cave with faggots and then setting them on fire.