The river Bille is a small, slow-flowing German river in Stormarn, Schleswig-Holstein and Hamburg, a right tributary of the Elbe. Its source is near Linau, north of the Hahnheide forest. It then flows south of Trittau, representing the border between Stormarn and Lauenburg, continues south of Reinbek and reaches the river Elbe near Billwerder. A lot of old estates and tasteful parks are laid out along its riverbank. Its total length is 65 km. Sections of the Bille which flow near or inside the Sachsenwald forest are protected by the Billetal nature reserve.