The
Duchy of Saxe-Lauenburg (, called
Niedersachsen (
Lower Saxony) between the 14th and 17th centuries), later also known as the
Duchy of Lauenburg, was a
reichsfrei duchy that existed 1296–1803 and 1814–1876 in the extreme southeast region of what is now
Schleswig-Holstein. Its territorial center was in the modern district of
Herzogtum Lauenburg and originally its eponymous capital was
Lauenburg upon Elbe, though in 1619 the capital moved to
Ratzeburg.