| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 461 | Mabon | Welsh | Legendary son of Modron. | M | |
| 462 | Mabsant | Welsh | Legendary son of Caw. | M | |
| 463 | Madawc | Welsh | Beneficent. | M | |
| 464 | Madawg | Welsh | Legendary son of Teithyon. | M | |
| 465 | Maddoc | Welsh | Beneficent. | M | |
| 466 | Maddock | Welsh | Beneficent. | M | |
| 467 | Maddockson | Welsh | Son of Maddock. | M | |
| 468 | Maddocson | Welsh | Son of Maddock. | M | |
| 469 | Maddog | Welsh | Beneficent. | M | |
| 470 | Maddox | Welsh | Son of Maddock. | M | |
| 471 | Madoc | Welsh | Fortunate. Beneficent. | M | |
| 472 | Madog | Welsh | Beneficent. | M | |
| 473 | Mael | Welsh | Legendary son of Roycol. | M | |
| 474 | Maelgwyn | Welsh | Prince of the hounds. | M | |
| 475 | Maelwys | Welsh | Legendary son of Baeddan. | M | |
| 476 | Mallolwch | Welsh | Legendary king of Ireland. | M | |
| 477 | Manawydan | Welsh | Legendary son of LIyr. | M | |
| 478 | March | Welsh | Legendary son of Meirchywn. | M | |
| 479 | Marvin | Welsh | Variant of Mervyn: Form of Merlin: From the sea fortress. | M | |
| 480 | Marvyn | Welsh | Variant of Mervyn: Form of Merlin: From the sea fortress. | M | |