NYKÖPING, a seaport-town of Sweden, capital of a Nyköping-län of the same name, stands on an inlet of the Baltic, 54 miles S.W. of Stockholm. It is regularly built, and contains a new and an old castle, several courts and public offices, three churches, an hospital, and manufactories of linen, cotton, and woollen stuffs, hosiery, tobacco, needles, &c. Pop. 3486. The län is bounded on the N. by Lake Mälare, which separates it from Upsala and Westeras, E. by Stockholm and the Baltic, S. by Linköping, and W. by Örebro. Area 2497 square miles. Many valuable minerals, such as iron, copper, lead, &c., are obtained here: the higher regions are well wooded, and the plains fertile and well cultivated. The bays on the Baltic coast facilitate the exportation of metals, timber, corn, and cattle. Pop. (1850) 120,113.