Diamanda Galás (born August 29, 1955) is an American avant-garde composer, vocalist, pianist, organist, performance artist, and painter.

Galás has been described as "capable of the most unnerving vocal terror", with her nearly five and a half (F2 to C#8) octave vocal range. Her works largely concentrate on the topics of AIDS, mental illness, despair, injustice, condemnation, and loss of dignity. She has worked with many avant-garde composers, including Iannis Xenakis, Vinko Globokar and John Zorn, and also collaborated with jazz musician Bobby Bradford, and John Paul Jones, former bassist of Led Zeppelin.