Royal Navy divers have confirmed that the object, which lies 32m (104ft) below the water’s surface, is a German-made torpedo.
While there is no risk to vessels in Scapa Flow, ships have been advised not to anchor near the discovered weapon.
The Royal Navy used Scapa Flow as a base in both world wars, meaning the seabed is now littered with British and German relics.
Divers often visit this spot to see the submerged antiques, including more than 50 German ships that were purposefully sunk by their commanders during World War One – to prevent them being appropriated by the Allies.
The Orkney Islands Council’s harbour master and head of marine services will decide how to safely dispose of the missile.
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