MMJ may refer to: Medical marijuana, cannabis prescribed by physicians for their patients , Filipino singing duo Modified Modular Jack, a six-pin modular connector used by Digital Equipment Corporation on their computers and peripherals. Moscow Mathematical Journal, a quarterly international academic journal published by the Independent University of Moscow My Morning Jacket, an American rock band The IATA airport code of Matsumoto Airport in Matsumoto, Nagano Prefecture, Japan The ISO 639-3 identifier code for the Majhwar language