'Barbara III' was a British unrealised naval operation to sink shipping in the Gulenfjord 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 designed for attachment by magnets to the target’s hull (6 February/16 March 1944).

An advance party was landed in 'Trace' on 6 February 1944 and began sending radio messages. The 'Barbara III' force sailed on 13 February but was forced back by bad weather. The operation was eventually abandoned, but the 'Trace' party continued to send messages until it was collected on 16 March by a submarine chaser.