MJ may refer to:

  • Manufacturers' Junction Railway's reporting mark
  • Líneas Aéreas Privadas Argentinas' IATA code
  • Jeep Comanche or MJ, a pickup truck
  • Millijoule (mJ) or megajoule (MJ), units of energy
  • MJ, a defunct New York City subway service
  • MJ, Jupiter mass, a unit of mass
  • Master of Jurisprudence, a graduate law degree
  • MJ, citation abbreviation for West's Military Justice Reporter
  • Marijuana

Read more about MJ:  People