'MB' (i) was the designation of Allied convoys (together with a numerical suffix) plying the route from Southampton to Brest with troops and equipment of the British Expeditionary Force for the reinforcement of France after the start of World War II (September/October 1939).

he first of the convoys was MB.1 of 10/12 September 1939 with the 6,574-ton British Castlemoor and 6,223-ton British Eurymedon, and the last was MB.10 of 1/2 October 1939 with unspecified ships.