| Mabon | | - | Welsh, Welsh Mythology | |
| Math | | - | Welsh Mythology | |
| Medraut | | - | Welsh Mythology, Arthurian Romance | |
| Medrod | | - | Welsh Mythology, Arthurian Romance | |
| Modred | | - | Welsh Mythology, Arthurian Romance | |
| Mordred | | - | Welsh Mythology, Arthurian Romance | |
| Myrddin | | - | Welsh Mythology | |