Un ballo in maschera (A Masked Ball) is an 1859 opera in three acts by Giuseppe Verdi. The text, by Antonio Somma, was based on Eugène Scribe's libretto for Daniel Auber's 1833 five act opera, Gustave III, ou Le bal masqué. The plot concerns the assassination in 1792 of King Gustav III of Sweden who was shot, as the result of a political conspiracy, while attending a masked ball, dying of his wounds thirteen days later..