| Name | Meaning | Gender | Origin |
|---|
| Mayhem | | Unisex | Hebrew |
| Melanctha | Black Flower | Female | Greek |
| Melanie | Black | Female | Greek |
| Mercy | Compassion | Female | English |
| Merle | Contracted form of Meriel | Female | English |
| Mickey | Who is like God? | Unisex | Hebrew |
| Midnight | Intense darkness, the middle of the night | Unisex | English |
| Missy | Bee | Female | Greek |
| Misty | Misty | Female | English |
| Molly | Uncertain, maybe bitter | Female | Hebrew |
| Moon | Letters | Female | Korean |
| Moonlight | | Unisex | Hebrew |
| Moonstruck | | Unisex | Hebrew |
| Moose | Largest member of the deer family. Moose have heavy brown bodies with humped shoulders and broad antlers. | Unisex | English |
| Mopsy | Term of affection, a darling. | Unisex | English |
| Mora | Peacock | Female | Sanskrit |
| Morag | Moor | Female | Latin |
| Morgan | Uncertain, perhaps bright sea | Female | Welsh |
| Moritz | Moor | Unisex | Latin |
| Mouse | A small rodent with a long tail and small rounded ears. | Unisex | English |
| Moxie | Ability to face difficulty with courage. | Unisex | English |
| Muffin | A small cup shaped cake | Unisex | English |
| Muffy | | Unisex | Hebrew |
| Nadia | Hope | Female | Russian |
| Ned | Wealth protector | Unisex | English |
| Neptune | God of the sea | Unisex | Latin |
| Nerissa | Sea sprite | Female | Greek |
| Nikki | Victory of the people | Female | Greek |
| Ninja | | Unisex | Hebrew |
| Obsidian | | Unisex | Hebrew |