Gieselau Canal, Summit level canal in Schleswig-Holstein, Germany.

The Gieselau Canal is a 2.8-kilometre waterway in Schleswig-Holstein linking the Kiel Canal with the River Eider. It runs from the Kiel Canal at kilometre 40.66 to the Eider at kilometre 22.75 and is navigable by vessels up to 65 metres long, 9 metres wide and 2.70 metres draught. The Gieselau lock, 65 metres long and 9 metres wide, sits about halfway along and evens out the water levels between the two waterways.

Built from 1936 to 1937, the canal replaced the old link through Rendsburg's town centre, where the 1893 Kiel Canal lock obstructed inner-city traffic. It runs from the Kiel Canal at Oldenbüttel to the Eider south of Prinzenmoor; the Rendsburg lock was subsequently filled in.

The canal takes its name from the Gieselau stream, whose old bed it crosses twice but otherwise does not follow. Since 1937 it has been a federal waterway, today used mainly by pleasure craft up to 65 m long, 9 m wide and 2.70 m draught.

The lock allows passage for boats when water levels differ between the two water bodies and is essential for transit. Visitors should know that crossing can take some time depending on current water conditions.

The canal does not follow the bed of the Gieselau stream, which was cut off by the Kiel Canal; it crosses the old channel only twice and shares nothing with the stream but its name. The Rendsburg lock was filled in after the canal opened.