A Symphony of Three Orchestras is an orchestra composition by the American composer Elliott Carter. The work was commissioned by the New York Philharmonic through a grant from the National Endowment for the Arts. It was composed from June through December 1976 and was first performed in New York City on February 17, 1977 by the New York Philharmonic under the conductor Pierre Boulez. The composition is dedicated to Boulez and the New York Philharmonic.