Geldern, a town of Prussia, in the province of the Rhine, on the Niers, 28 m. N. W. of Dusseldorf; pop. in 1871, 5,096. It has a Catholic and a Protestant church, two convents, manufactures of cloth, stockings, hats, woollen, silk, and linen goods, and a considerable trade in grain. The town was built in 1097, and was till 1343 the residence of the counts and dukes of Geldern. (See Gelderland.) Its fortifications were razed by Frederick the Great in 1764.