Lauenburg (louˈənbŏrkh) [key], former duchy, NE central Germany, on the right bank of the lower Elbe. The duchy belonged to a branch of the house of Saxony from the 12th to the late 17th cent., when it passed to the house of Hanover. Lauenburg was occupied by France from 1803 to 1813. The Congress of Vienna awarded (1815) it to Prussia and made it a member state of the German Confederation, but Prussia ceded it to the Danish crown in exchange for W Pomerania. In the Danish War of 1864 the duchy was seized by Prussia and Austria, and Austria soon afterward ceded its rights to Prussia. Lauenburg was incorporated into the province of Schleswig-Holstein in 1876 and ceased to be a duchy in 1918.