Wandse (in sections also called Eilbek) is a river of Hamburg, Germany. The Wandse rises west of the village of Siek in Kreis Stormarn in Schleswig-Holstein and ends in the center of Hamburg in the Alster. Along the banks of the Wandse there were many water mills. The river passes through the settlements of Siek, Braak, Stapelfeld, and Hamburg.
In Hamburg, the district of Wandsbek takes it name from the river as it winds its way westwards via Eichtal Park. After passing through the Mühlenteich, the river continues as Eilbek (later Eilbekkanal), eponymous to the Eilbek district. The canal joins the Alster in the heart of Hamburg at Außenalster.