What was mozarts LONGEST piece of music?

The longest piece of music composed by Wolfgang Amadeus Mozart is the opera "La clemenza di Tito", K. 621. This opera seria in two acts was completed in 1791 and premiered in Prague on September 6 of the same year. It is based on the libretto by Pietro Metastasio and tells the story of the Roman emperor Titus, who shows mercy to those who have conspired against him. The opera consists of 33 musical numbers and has a total duration of approximately 3 hours and 30 minutes, making it the longest piece of music composed by Mozart.