OELS, a town of Prussia, in the government of Breslau, on the Oelsa, 17 miles N.N.E. of Breslau. It is fortified; and has an extensive ducal palace built in the form of a square, and containing a good library; a Roman Catholic and three Protestant churches, a synagogue, several schools, an hospital, and a theatre. Manufactures of woollen, linen, and silken stuffs are carried on here; and there are oil and other mills. Pop. 6928.