The Sinful Border (German: Sündige Grenze) is a 1951 West German crime film directed by Robert A. Stemmle and starring Dieter Borsche, Inge Egger and Peter Mosbacher. Jan Hendriks won the German Film Award as Best Newcomer. It focuses on the smuggling of coffee, at the time an expensive luxury, into Germany. It is also known by the alternative title of Illegal Border.

It was shot at the Spandau Studios in Berlin and on location in the Harz Mountains. The film's sets were designed by the art directors Mathias Matthies and Ellen Schmidt.