| Micronesia, Federated States of |
|
| Middle Congo |
|
| Minnesota (MN) |
|
| Mississippi (MS) |
|
| Missouri (MO) |
|
| Modena |
|
| Moheli |
|
| Moldova |
|
| Monaco |
|
| Mongolia |
|
| Montana (MT) |
|
| Montenegro |
|
| Montenegro, Italian Occupation |
|
| Montserrat |
|
| Morocco |
|
| Morocco, British Post Office |
|
| Morocco, French Protectorate |
|
| Morocco, German Post Offices |
|
| Morvi |
|
| Mozambique |
|