a town of Germany, in the Prussian province of Hesse-Nassau, delightfully situated in the midst of a well-wooded country, on the Dill, 25 m. N.W. from Giessen on the railway to Troisdorf. Pop. 4500. On an eminence above it lie the ruins of the castle of Dillenburg, founded by Count Henry the Rich of Nassau, about the year 12J5, and the birthplace of Prince William of Orange (1533). It has an Evangelical church, with the vault of the princes of Nassau-Dillenburg, a Roman Catholic church, a classical school, a teachers' seminary and a chamber of commerce. Its industries embrace iron-works, tanneries and the manufacture of cigars. Owing to its beautiful surroundings Dillenburg has become a favourite summer resort.