Nykøbing (nü`kö'bĭng), city (1992 com. pop. 25,350), capital of Storstrøm co., SE Denmark, on Falster Island and on the Guldborg Sund, connected by bridge with Lolland. It is a seaport and has sugar refineries, breweries, shipyards, and textile mills. Of note are a Gothic church (until 1532 a Franciscan monastery) and the ruins of a 12th-century castle.