John Michael Erlewine (/ˈɜːrlwaɪn/; born July 18, 1941) is an American musician, astrologer, photographer, publisher, and Internet entrepreneur who founded the music online database site AllMusic (previously known as All Music Guide) in 1991.

Erlewine has had several careers. As a musician, he was active in the Michigan folk scene in the late 1950s and early 1960s. In 1961, he hitchhiked with Bob Dylan, and traveled to Greenwich Village in Lower Manhattan, New York; Venice, a Los Angeles neighborhood; and San Francisco. He and his brother Dan began a blues band called the Prime Movers, which regularly played in Chicago; other members included "Blue" Gene Tyranny (Robert Sheff). When the drummer left, the band replaced him with Iggy Pop (James Osterberg), then 18 years old. The Prime Movers gave him the nickname "Iggy" as he had played in the band The Iguanas. According to biographer Jim Ambrose, the two years Osterberg which was in the band made him aware of "art, politics, and experimentation."

In 1977, Erlewine founded Matrix Software. He was the first person to program astrology on microcomputers and make astrological programs available to the astrological community. He has published more than forty books on astrology and related topics. Michael Erlewine and his band, the Prime Movers, were inducted into the Michigan Rock and Roll Legends Hall of Fame in 2015.

Erlewine and his wife have four children including musician May Erlewine. He is the uncle of music critic Stephen Thomas Erlewine.

In the 1990s, Erlewine founded the All Music Guide (allmusic.com), the All Movie Guide (allmovie.com), and the All Game Guide (allgame.com). The first site in particular has become an important popular music reference which licenses its content to numerous other websites. Erlewine regained control of Matrix Software (astrologysoftware.com) in November 2008 and is the director of the company.