Hardegsen is a town in the district of Northeim, in Lower Saxony, Germany. It is situated approximately 15 km southwest of Northeim, and 15 km northwest of Göttingen.Burg Hardeg is a medieval castle in Hardegsen. The castle was founded in the 12th century as a residence of the House of Welf. In the 1320 the stone castle was rebuilt by Conrad und Ludwig von Rosdorf. In the end of the 14th century the castle passed to Otto von Braunschweig zu Göttingen.