Kustrin, Or Custrin, a town of Prussia, in the province of Brandenburg, near the junction of the Warthe with the Oder, which is spanned by a bridge about 900 ft. long, on the railway from Berlin to Dantzic, 48 m. E. of the former city; pop. in 1871, 10,122, exclusive of the garrison. It is a fortress of the third rank, and contains three suburbs, a royal palace, two churches, a gymnasium, and several other schools. In the vicinity are many sugar refineries, and the local and coasting trade is active. It was founded early in the 16th century, and became the capital of the Neumark and of the margrave John, known as John of Kustrin and as John the Wise, a zealous reformer, who built the fortress and the palace, covering the latter with copper. Frederick the Great, while crown prince, was confined here for a time by his father; and Lieut. Katt, his intimate friend and alleged accomplice in his proposed flight to England, was beheaded here, Nov. 6, 1730. The fortress was bombarded by the Russians, Aug. 15-22, 1758, and saved only from utter destruction by Frederick the Great. Soon after the battle of Jena (1806) the Prussian commander hastily surrendered it, though it had sufficient provisions to hold out for a long time; and the French occupied it till early in 1814, when they capitulated.