Nienburg is a Kreis (district) in the southern part of Lower Saxony, Germany. Area 1399 km², population 126,300 (2001). The district's capital is Nienburg[?].
The district is roughly located between Bremen and Hanover. The Weser river enters the district in the south, coming from North Rhine-Westphalia, and runs north towards Bremen. In medieval times the territory of the today's district was the eastern part of the county of Hoya; the town of Hoya[?], at that time a powerful city, is located in the north of the district.
Towns in the district: Nienburg[?], Rehburg-Loccum[?], Hoya[?].