Arboga (ärˈbōˌgä) [key], town (1990 pop. 11,548), Västmanland co., S Sweden, on the Arboga River, near Lake Hjälmaren. It is a transportation, industrial, and tourist center. Manufactures include metal goods and processed food. Of great importance in the Middle Ages, Arboga was the site of several parliaments, including Sweden's first (1435), and numerous church assemblies. St. Bridget was proclaimed patron saint of Sweden there in 1396. The city has a Franciscan monastery (founded 1285).