South Lower Saxony refers to the southern part of the German federal state of Lower Saxony. The region so described is neither historically nor geographically clearly defined to the north within Lower Saxony. It cuts across the more obviously delineated natural regions of the Weser Uplands, Leine valley, Leine Uplands and the western parts of the Harz mountains as well as the western part of the historical region of Eichsfeld.