- Mackenzie River husky
- Magyar Agar
- Maltese
- Maltese Shitzu
- Maltipoo
- Manchester Terrier
- Maremma Sheepdog
- Mastiff – see English Mastiff
- McNab
- Meliteo Kinidio
- Mexican Hairless Dog
- Miniature Australian Shepherd
- Miniature Fox Terrier
- Miniature Pinscher
- Miniature Schnauzer
- Mioritic
- Mixed-breed dog
- Moscovskaya Storozhevaya Sobaka (Moscow Watchdog)
- Mountain Burmese
- Mountain Cur
- Mudi
- Mudhol Hound
- Munsterlander (Large Munsterlander, Small Munsterlander)