MJ may refer to:
Mjolnir ( 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.
Mjøsa is Norway's largest lake, as well as one of the deepest lakes in Norway and in Europe. It is the fourth-deepest lake in Norway.
MJM Music PL, is a Polish independent record label founded in 1990 in Warsaw by Polskie Radio journalist Andrzej Wojciechowski.
MJP Architects is an employee-owned British architectural practice established in 1972 by Sir Richard MacCormac, and based in Spitalfields, London.
Mjini Magharibi Region (also known as the Zanzibar Urban West Region) is one of the 31 regions of Tanzania.