Sardanapalo or Sardanapale, S.687, is an unfinished opera by Franz Liszt based on the 1821 verse play Sardanapalus by Lord Byron. Liszt was ambitious for his project, and planned to dovetail his retirement as a virtuoso with the premiere of his opera. He worked on it intermittently between 1845 and 1852, once declaring it 'well on the way toward completion,' but ceased work on it thereafter. The first act had been completed in a detailed, continuous particell, but there is no evidence of any music being notated for Acts 2–3. As an Italian opera, it would almost certainly have been called Sardanapalo, though Liszt referred to it as Sardanapale in his French correspondence. The music Liszt completed remained silent until 2016 when British musicologist David Trippett first established the legibility of Liszt's N4 manuscript, and produced both a critical edition and realized an orchestral performing edition. This received its world premiere in Weimar on 19 August 2018.

Don Sanche, ou Le château de l'amour, S.1, is an opera in one act composed in 1824–25 by Franz Liszt in his early teen years, with French libretto by Théaulon and de Rancé, based on a story by Jean-Pierre Claris de Florian. For 30 years it was believed to be lost until it was rediscovered in 1903. The first modern performance took place in 1977, 74 years after its rediscovery.