Bomarzo is an opera in two acts by Alberto Ginastera, his Opus 34, to a Spanish libretto by Manuel Mujica Laínez, based on his 1962 novel about the 16th-century Italian eccentric Pier Francesco Orsini. The opera had its world premiere at the Opera Society of Washington, Washington D.C., on 19 May 1967. The same production was first given at New York City Opera on 14 March 1968. The work had been scheduled for its first performance in Argentina on 4 August 1967 at the Teatro Colón, but the Argentine president, Juan Carlos Onganía, had banned the production, objecting to the sexual content of the story. The first performance in Argentina did not occur until 1972, with the composer in attendance. The first UK production was at English National Opera on 3 November 1976, in an English translation by Lionel Salter.

The opera makes use of the twelve-tone technique and quarter tones, the latter primarily in the harp parts. The work's two acts encompass a prelude and 15 scenes. Pola Suarez Urtubey has published an analysis of the opera with an outline of the dramatic structure.