Oels, a town of Prussian Silesia, in a valley on the Oelsa, 10 m. N. E. of Breslau; pop. in 1871, 8,124. It contains a media)val castle, in a park surrounded by a wall and moat, with gardens and a picture gallery; a Catholic and four Protestant churches, a synagogue, a Protestant gymnasium, a theatre, and a retreat for the widows of clergymen. There are extensive manufactories of cloth. In the vicinity are the villages and ducal villas of Wilhel-minenort and Sibyllenort. It is the capital of a mediatized principality, formerly a duchy, including Oels-Bernstadt, besides the circles of Oels and Trebnitz, the domain of Medzibor, and the town and district of Konstadt; aggregate pop. about 170,000. The duchy of Oels originally belonged to the dukes of Silesia, and after passing through many hands the right of succession to it was conceded by Frederick the Great in 1785 to the duke Frederick William of Brunswick, who fell in 1815 in the battle of Quatre-Bras. His son Charles ceded it in 1824, under the name of Brunswick-Oels, to his brother William, the present duke of Brunswick.