Ploen, a town of Germany, in Schleswig-Holstein, beautifully situated between two lakes, the large and the small Ploener-See, 20 m. S. from Kiel by the railway to Eutin and Lubeck. Pop. (1905), 3735 It has a palace built about 1630 and now converted into a cadet school, a gymnasium and a biological station. Tobacco, soap, soda, beer and furniture are manufactured, and there is a considerable trade in timber and grain. The lakes afford good fishing, and are navigated in summer by steamboats.
Ploen is mentioned as early as the 11th century as a Wendish settlement, and a fortified place. It passed in 1559 to Duke John the Younger, founder of the line of Holstein-Sonderburg, on the extinction of which, in 1761, it fell to Denmark, and in 1867, with Schleswig-Holstein, to Prussia. The sons of the emperor William II. received their early education here.
See H. Eggers, Schloss and Stadt Ploen (Kiel, 1877), and J. C. Kinder, Urkundenbuch zur Chronik der Stadt Ploen (Plon, 1890).
