La clemenza di Tito (English: The Clemency of Titus), K. 621, is an opera seria in two acts composed by Wolfgang Amadeus Mozart to an Italian libretto by Caterino Mazzol , after Metastasio. It was started after the bulk of Die Zauberflöte (The Magic Flute), the last opera that Mozart worked on, was already written. The work premiered on 6 September 1791 at the Estates Theatre in Prague.