Wolfgang Amadeus Mozart was a composer of Terran western classical music. Mozart is considered by many to be among the greatest of Terran composers, having written masterpieces in every genre of his day: symphonies, operas, masses, keyboard sonatas, piano and other concertos, string quartets, and other chamber works.
The Traveler compared the skills of Wesley Crusher with those of Mozart when he talked to Captain Picard of the USS Enterprise-D. (TNG: "Where No One Has Gone Before")
A little later, a crewmember of the Enterprise-D fantasized playing Eine kleine Nachtmusik on the violin, together with three other musicians dressed in period clothing. (TNG: "Where No One Has Gone Before")
Vulcan Ambassador Sarek and his wife, Perrin, were fond of Mozart's music, as both attended a concert performed aboard the Enterprise-D in 2366. (TNG: "Sarek")
- Oddly enough, one of the pieces at the recital was actually by Johannes Brahms.
In 2368, Data listened to Mozart's Jupiter symphony in C major in order to analyze its aesthetics. (TNG: "A Matter of Time")
Captain Picard enjoyed performing chamber works by Mozart on his Ressikan flute. His Picard Mozart trio featured the addition of his flute composition to a previous Mozart work. (TNG: "A Fistful of Datas")
Captain Kathryn Janeway, as Lucille Davenport on the holodeck, heard someone play a lovely Mozart sonata in the music room of Lord Burleigh's mansion and thought Beatrice Burleigh played the piece. The Lord was confused, however, as Lucy didn't play the piano. (VOY: "Persistence of Vision")
Harry Kim had troubles hitting the G-sharp in a certain Mozart concerto, as he was reminded by the Clown. (VOY: "The Thaw")
Charles Tucker III introduced the Cogenitor to a piece of music by Mozart. (ENT: "Cogenitor")
- In an alternate timeline, the Doctor chose Mozart as his name. (VOY: "Before and After")