- Malfunction (mechanism or component) (of),
- Maltreatment, see Perpetrator
- Mangled NOS (accidentally), X58
- Manhandling (in brawl, fight), Y04.0
- Manslaughter (nonaccidental), see Assault
- Mauled by animal NEC, W55.89
- Medical procedure, complication of (delayed or as an abnormal reaction without mention of misadventure), see Complication of or following, by specified type of procedure
- Melting (due to fire), see Exposure, fire
- Mental cruelty, X58
- Military operations (injuries to military and civilians occuring during peacetime on military property and during routine military exercises and operations) (by) (from) (involving), Y37.90-
- Misadventure during surgical or medical care (s) to patient(s), Y69
- Mismatched blood in transfusion, Y65.0
- Motion sickness, T75.3
- Mountain sickness, W94.11
- Mudslide (of cataclysmic nature), see Landslide
- Murder (attempt), see Assault