The Welman submarine was a Second World War one-man British midget submarine developed by the Special Operations Executive. It only saw action once and was not particularly successful.

A midget submarine is any submarine under 150 tons, typically operated by a crew of one or two but sometimes up to six or nine, with little or no on-board living accommodation. They normally work with mother ships, from which they are launched and recovered and which provide living accommodation for the crew and support staff.