Mary Jane Leach (born 1949) is an American composer based in New York City.

As her music became more frequently performed she continued writing in an "overdubbing" fashion, layering parts and experimenting with the textures created by multiple voices.

[4] Leach received a 1995 Foundation for Contemporary Arts Grants to Artists Award.

Leach is also the primary archivist and bibliographer of composer Julius Eastman.

[6] In the late 1990s, she realized his music had been lost and set about collecting scores and recordings.