| Mererid | Woman | Welsh Names |
| Merewyn | Man | Welsh Names |
| Meriadoc | Man | Welsh Names |
| Merlyn | Woman | Welsh Names |
| Mervin | Man | Welsh Names |
| Mervyn | Man | Welsh Names |
| Meurig | Man | Welsh Names |
| Mihangel | Man | Welsh Names |
| Mordred | Man | Welsh Names |
| Morgan | Unisex | Welsh Names |
| Morgana | Woman | Welsh Names |
| Morwen | Woman | Welsh Names |
| Mostyn | Unisex | Welsh Names |
| Myfanwy | Woman | Welsh Names |
| Myrddin | Man | Welsh Names |