Västerås, city in eastern Sweden, on an arm of Lake Mälaren, at the mouth of the Svart River (Svartån). The capital of Västmanland County and a road and railroad hub, the city is the center of the Swedish electrical industry; manufactures include appliances, iron and steel, generators and motors, locomotives, glass, and lumber products. Of interest are a Gothic cathedral, built in 1271 on the site of an 11th-century church, which contains the tomb of Eric XIV, king of Sweden; a reconstructed 12th-century castle once captured by Gustav I Vasa, king of Sweden; a noted episcopal library; a county folk museum; an industrial museum; and the Djakneberget, a park containing statues of historical personages.
A trade and cultural center in the Middle Ages, the city was originally called Aros; the name was changed to Västra (Vestra) Aros in 1271. In 1527 the parliament produced the Västerås Recess, which introduced the Reformation to Sweden and placed the church under the control of Gustav I Vasa and the state. In 1544 the hereditary law of accession to the throne was adopted in the city. Its name was also formerly spelled Vesterås or Westerås. Population (1998 estimate) 124,780.
