| Name | Gender | Pronounced | Usage | Popularity |
|---|---|---|---|---|
| Martyn | - | Welsh, Ukrainian | ||
| Math | - | Welsh Mythology | ||
| Maxen | - | Welsh (Anglicized) | ||
| Medraut | - | Welsh Mythology, Arthurian Romance | ||
| Medrod | - | Welsh Mythology, Arthurian Romance | ||
| Megan | MEG-ən (English) | Welsh, English | ||
| Meical | - | Welsh | ||
| Meinir | - | Welsh | ||
| Meinwen | - | Welsh | ||
| Meirion | - | Welsh | ||
| Meiriona | - | Welsh | ||
| Meredith | MER-ə-dith (English) | Welsh, English | ||
| Meredydd | - | Welsh | ||
| Mererid | - | Welsh | ||
| Merfyn | - | Welsh |