M84 or M-84 may refer to:
- Messier 84, a galaxy in the Virgo Cluster
- M-84, a Yugoslav main battle tank
- M84 machine gun, Yugoslavia
- M84 camouflage pattern, used by the Danish Army
- M84 stun grenade, a non-lethal grenade
- 152 mm field gun-howitzer M84 NORA-A, Yugoslavia
- M-84 (Michigan highway), a US state highway
- M84 mortar carrier, a modified armored personnel carrier