MJ may refer to:
Mary "MJ" Jennings Hegar (née von Stein; born 1976) is an American Air Force veteran, businesswoman, and teacher.
Mj Rodriguez (born January 7, 1991; sometimes capitalized as MJ Rodriguez) is an American actress and singer.
Mjolnir () is a fictional mythical 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.
MJ Erb (born February 2, 1994) is an American long-distance runner born in Farmington, New York.