Büchen is a municipality in the district of Lauenburg, in Schleswig-Holstein, Germany. It is seat of the Amt ("collective municipality") Büchen.
Büchen is situated on the Elbe-Lübeck Canal, approx. 13km northeast of Lauenburg/Elbe, and 45km east of Hamburg. Büchen station is on the Berlin-Hamburg and the Lübeck–Lüneburg lines.