| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 581 | Morgane | Celtic | Dweller of the sea. | F | |
| 582 | Morna | Celtic | Dearly loved or tender. | F | |
| 583 | Morrigan | Celtic | A war goddess. | F | |
| 584 | Morven | Celtic | Lives by the sea. | M | |
| 585 | Morvyn | Celtic | Lives by the sea. | M | |
| 586 | Moryn | Celtic | Lives by the sea. | M | |
| 587 | Moya | Celtic | Exceptional. | F | |
| 588 | Moyna | Celtic | Tender or mild. | F | |
| 589 | Mungo | Celtic | Lovable. | M | |
| 590 | Murdoc | Celtic | Seaman. | M | |
| 591 | Murdoch | Celtic | Seaman. | M | |
| 592 | Murdock | Celtic | Seaman. | M | |
| 593 | Muriel | Celtic | Shining sea. | F | |
| 594 | Murray | Celtic | Lives by the sea. | M | |
| 595 | Murry | Celtic | Lives by the sea. | M | |
| 596 | Murtagh | Celtic | Protects the sea. | M | |
| 597 | Mynogan | Celtic | Mythical father of Beli. | M | |
| 598 | Myrna | Celtic | Tender. | F | |
| 599 | Naois | Celtic | Mythical warrior. | M | |
| 600 | Nara | Celtic | Contented. | F | |