Deventer, city (1994 pop. 69,079), Overijssel prov., E central Netherlands, on the IJssel River. It is an industrial center with machine shops and foundries; important manufactures are bicycles and bricks. A member of the Hanseatic League in the Middle Ages, it was a prosperous commercial city and a center of piety and learning; Thomas à Kempis and Erasmus of Rotterdam studied there. Deventer has retained many medieval and Renaissance structures, including the Groote Kerk (church, built 8th cent., and later rebuilt), the Mariakerk (15th cent.), the weighhouse (16th cent.), and the town hall (17th cent.).