NYBORG, a seaport of Denmark on the east side of the island of Fünen, in the amt (county) of Svendborg, and the point from which the ferry crosses the Great Belt to Korsör in Zealand (15 m.). Pop. (1901) 7790. The fortress, built by Christian IV. and Frederick III., was dismantled in 1869, and the ruins of the castle are used as a prison. In the 12th century the town was founded and a castle erected on Knudshoved (Canute's Head) by Knud, nephew of Waldemar the Great, and from the 13th to the 15th century Nyborg was one of the most important places in Denmark. In 1658 it surrendered to the Swedes; but by the defeat of the latter under the walls of the fortress on the 24th of November 1659, the country was freed from their dominion. In 1808 the Marquis La Romana, who with a body of Spanish troops garrisoned the fortress for France, revolted from his allegiance, and held out till he and a portion of his men escaped with the English fleet.