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).

The premiere took place a few hours after Leopold's coronation. The role of Sesto was taken by castrato soprano, Domenico Bedini. The opera was first performed publicly on 6 September 1791 at the Estates Theatre in Prague.

The opera remained popular for many years after Mozart's death. It was the first Mozart opera to reach London, receiving its première there at His Majesty's Theatre on 27 March 1806.The cast included John Braham whose long-time companion Nancy Storace, had been the first Susanna in Le Nozze di Figaro in Vienna. However as it was only played once it does not appear to have attracted much interest. As far as can be gathered it was not staged in London again until at the St Pancras Festival in 1957. The first performance at La Scala in Milan was on 26 December 1818. The North American premiere was staged on 4 August 1952 at the Berkshire Music Center in Tanglewood. But for a long time, Mozart scholars regarded Tito as an inferior effort of the composer. Alfred Einstein in 1945 wrote that it was "customary to speak disparagingly of La clemenza di Tito and to dismiss it as the product of haste and fatigue," and he continues the disparagement to some extent by condemning the characters as puppets – e.g., "Tito is nothing but a mere puppet representing magnanimity" – and claiming that the opera seria was already a moribund form. However, in recent years the opera has undergone something of a reappraisal. Stanley Sadie considered it to show Mozart "responding with music of restraint, nobility and warmth to a new kind of stimulus".

The opera continues to be popular: Operabase lists 89 performances of 17 productions in 16 different cities for 2011 and 2012.