'Barbara IV' was a British unrealised naval operation to sink shipping in the Syvdefjord of German-occupied Norway using 'Welman' one-man electrically powered submersible craft each weighing some 2,000 lb (907 kg) excluding the 425-lb (193-kg) Torpex warhead, which was attached magnetically to the target’s hull (February/March 1944).

The object was also to supply intelligence using the Special Operations Executive station in Ålesund, but the operation did not take place.