| # | Name | Origin | Meaning | Gender | |
|---|---|---|---|---|---|
| 681 | Meirion | Welsh | Name derived from the old county of Merionethshire. | M | |
| 682 | Menw | Welsh | Legendary son of Teinkaedd. | M | |
| 683 | Mercher | Welsh | Welsh form of Mercury, messenger of the gods. | M | |
| 684 | Mercia | Welsh | From Mercia. | F | |
| 685 | Meredith | Welsh | Magnificent. Great chief. Great lady. This name can be given to children of either gender, but is more common among girls. | F | |
| 686 | Meredith | Welsh | Guardian of the sea. Great chief. This name can be given to children of either gender, but is more common among girls. | M | |
| 687 | Meredydd | Welsh | Magnificent. | F | |
| 688 | Meredydd | Welsh | Guardian of the sea. | M | |
| 689 | Mererid | Welsh | Pearl. | F | |
| 690 | Meridith | Welsh | Guardian of the sea. | M | |
| 691 | Merlin | Welsh | Hawk. From the sea fortress. In Arthurian legend, Merlin Ambrosius was adviser/mentor to King Arthur. | M | |
| 692 | Merlyn | Welsh | Sea fortress. In Arthurian mythology the wizard Merlin was King Arthur's mentor. | M | |
| 693 | Merrick | Welsh | Dark-skinned; A Moor. Form of Maurice. | M | |
| 694 | Merrion | Welsh | Variant of Meirion: Name derived from the old county of Merionethshire. | F | |
| 695 | Merrion | Welsh | Variant of Meirion: Name derived from the old county of Merionethshire. | M | |
| 696 | Merry | Welsh | Diminutive of Meredith: Magnificent. Great chief. Great lady. Used for both genders, but most common among girls. | F | |
| 697 | Merry | Welsh | Diminutive of Meredith: Guardian of the sea. Great chief. This name can be given to children of either gender, but is more common among girls. | M | |
| 698 | Merv | Welsh | Diminutive of Mervyn: Form of Merlin: From the sea fortress. | M | |
| 699 | Mervin | Welsh | Variant of Mervyn: Form of Merlin: From the sea fortress. | M | |
| 700 | Mervyn | Welsh | Form of Merlin: From the sea fortress. | M | |