The County of Dannenberg (German: Grafschaft Dannenberg) was a fief in the Duchy of Saxony. Its heartland was largely identical with the present-day collective municipality of Elbtalaue in north Germany. Its historical origins go back to the middle of the 12th century, when Henry the Lion founded the five counties of Holstein, , Schwerin, Dannenberg and Lüchow during the Ostsiedlung, or colonisation of the East, from the mouth of the River Elbe to the southern border of the March of Brandenburg, in order to protect the new regions and borders of his territory.