MJ may refer to:
Mjolnir (/ˈmoʊlnᵻr/ MOHL-n(ee)r) is a fictional weapon appearing in American comic books published by Marvel Comics.
mjunction services limited is a 50:50 joint venture of two Indian steel conglomerate – the Steel Authority of India Ltd (SAIL) and Tata Steel.
MJM Music PL, is a Polish independent record label founded in 1990 in Warsaw by Polskie Radio journalist Andrzej Wojciechowski.
Mjini Magharibi Region (also known as the Zanzibar Urban West Region) is one of the thirty regions of Tanzania.
MJP Architects is an employee-owned British architectural practice established in 1972 by Sir Richard MacCormac, and based in Spitalfields, London.
Mjällby Allmänna Idrottsförening, also known simply as Mjällby AIF, Mjällby or (especially locally) MAIF, is a Swedish professional football club based in Hällevik.