The O class was a planned class of three battlecruisers for the Kriegsmarine (German Navy) before the Second World War. Prompted by a perceived lack in ship numbers when compared with the British Royal Navy, the O class' design was born with the suggestion of modifying the P-class cruiser design with guns instead of . The ships were incorporated into the 1939 Plan Z; while an aircraft carrier, H-class battleships and smaller ships engaged convoy escorts, one or more O-class ships would attack the merchant ships.