ARNSBERG, a town in Westphalia, Germany, built on high ground almost surrounded by the river Ruhr, 44m. S.S.E. of Munster. Pop. (1933) 12,080. Near by are the ruins of the castle of the counts of Arnsberg. It received its first charter in 1237 and later joined the Hanseatic league. It is the seat of the provincial authorities, and has a chamber of commerce. Paper is made.