Osterode is a Kreis (district) in the southeastern part of Lower Saxony, Germany. It comprises the southwestern part of the Harz mountains. Area 636 km², population 85,500 (2000). The capital of the district is Osterode.
More than two thirds of the district's area are occupied by the Harz mountains, including the southern portion of the Harz National Park.
Towns in the district: Osterode, Herzberg, Bad Lauterberg, Bad Sachsa, Bad Grund.