- Margam
- Marian
- Marianglas
- Markham
- Marloes
- Marros
- Marshfield
- Martletwy
- Mascle Bridge
- Mathern
- Mathry
- Mawdlam
- Meidrim
- Meifod
- Meinciau
- Meliden
- Melin-y-coed
- Melincourt
- Menai Bridge
- Merlin's Bridge
- Merrion
- Merthyr
- Merthyr Cynog
- Merthyr Mawr
- Merthyr Tewdrig
- Merthyr Tydfil
- Merthyr Vale
- Meyllteyrn
- Michaelston-le-Pit
- Middle Mill