MJ may refer to:
Mj Rodriguez (born January 7, 1991; sometimes capitalized as MJ Rodriguez) is an American actress and singer.
Mary "MJ" Jennings Hegar (née von Stein; born 1976) is an American politician, Air Force veteran, businesswoman, and teacher.
Mjolnir () is a fictional mythical weapon appearing in American comic books published by Marvel Comics.
MJ Cole (born Matthew James Firth Coleman, 9 August 1973) is an English DJ, record producer, musician and remixer.
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.
Mjötviður Mær, released in 1981, was the second album by Icelandic new wave/rock group Þeyr. It was edited through Eskvímó in 12” vinyl.
Mjällby Allmänna Idrottsförening, also known simply as Mjällby AIF, Mjällby or (especially locally) MAIF, is a Swedish professional football club based in Hällevik.