| MCEM 3 | |
| Origin: | United Kingdom |
| Type: | Submachine gun |
| Is Ranged: | YES |
| Designer: | Royal Small Arms Factory |
| Design Date: | 1947 |
| Action: | Blowback |
| Sights: | Fixed |
The MCEM 3 was a proposed collapsible 9mm submachine gun designed by the British in 1947. It had a detachable stock alongside the magazine and a Lee–Enfield type bayonet. However the MCEM 3 was not accepted and found no customers.