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 Metastasio. It was started after the bulk of The Magic Flute, the last opera that Mozart worked on, was already written (Mozart completed The Magic Flute after the Prague premiere of Tito on 6 September 1791).

In July 1791, the last year of his life, Mozart was already well advanced in writing The Magic Flute when he was asked to compose an opera seria. The commission came from the impresario Domenico Guardasoni, who lived in Prague and who had been charged by the Estate of Bohemia with providing a new work to celebrate the coronation of Leopold II, Holy Roman Emperor as King of Bohemia. The ceremony was to take place on 6 September; Guardasoni had been approached about the opera in June. There was not much room to manoeuvre.

In a contract dated 8 July, Guardasoni promised that he would engage a castrato "of leading quality" (this seems to have mattered more than who wrote the opera); that he would "have the libretto caused to be written...and to be set to music by a distinguished maestro". The time was tight and Guardasoni had a get-out clause: if he failed to secure a new text, he would resort to La clemenza di Tito, a libretto written more than half a century earlier by Pietro Metastasio (1698–1782).

Wolfgang Amadeus Mozart (German: [ˈvɔlfɡaŋ amaˈdeus ˈmoːtsaʁt], English see fn.), baptismal name Johannes Chrysostomus Wolfgangus Theophilus Mozart (27 January 1756 – 5 December 1791), was a prolific and influential composer of the Classical era. He composed over 600 works, many acknowledged as pinnacles of symphonic, concertante, chamber, operatic, and choral music. He is among the most enduringly popular of classical composers.

Mozart showed prodigious ability from his earliest childhood in Salzburg. Already competent on keyboard and violin, he composed from the age of five and performed before European royalty. At 17, he was engaged as a court musician in Salzburg, but grew restless and travelled in search of a better position, always composing abundantly. While visiting Vienna in 1781, he was dismissed from his Salzburg position. He chose to stay in the capital, where he achieved fame but little financial security. During his final years in Vienna, he composed many of his best-known symphonies, concertos, and operas, and portions of the Requiem, which was largely unfinished at the time of his death. The circumstances of his early death have been much mythologized. He was survived by his wife Constanze and two sons.