The London Underground M Stock and N Stock were similar designs of rolling stock built in 1935. As the new cars were urgently required they were based on existing L Stock. Several years after construction both types were absorbed into the Q Stock. The last of these trains were withdrawn in 1971.
The M Stock was the first surface stock to be delivered with air-operated doors.
Upon conversion to Q Stock, all the cars were transferred to the District line (with the Hammersmith and City Line services being operated from 1938 onwards by new trains of O Stock).