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 Mazzolà, after Pietro 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.