Dęblin (dĕNˈblēn) [key], city (1994 est. pop. 19,400), Lubelskie prov., E Poland, on the Vistula River. It is a railway junction and one of the main crossings of the Vistula. Founded as a fortress by Czar Nicholas I in 1837, it was captured by the Germans in 1915 but was returned to Poland after World War I.