'MD5' was a British naval diversionary undertaking by ships of Admiral Sir Andrew Cunningham’s Mediterranean Fleet to ease the passage of the 'Substance' convoy supervised by Vice Admiral Sir James Somerville’s Gibraltar-based Force 'H' (23/25 June 1941).

The ships involved were the battleships Queen Elizabeth and Valiant, the light cruisers Ajax, Leander, Neptune and Australian Hobart, the light anti-aircraft cruisers Carlisle, Naiad and Phoebe, and the cruiser minelayers Abdiel and Latona.