Aalst (älst) [key], Fr. Alost, city (1991 pop. 76,382), East Flanders prov., W central Belgium. Aalst is a commercial and industrial center. Manufactures include textiles, clothing, and footwear. Known since the 9th cent., Aalst was held by France from 1667 to 1706 and was the capital of the county of Flanders under the Austrians in the 18th cent. Of note are the city hall (13th cent.) and the Church of St. Martin (15th cent.), which contains a painting by Peter Paul Rubens.