The forgotten composer and opera singer, Prince Józef Michal Ksawery Poniatowski (1816-1873), a well-known figure in the political and musical world of Italy and France born in Rome, worked as Tuscan ambassador and became a senator of the French empire at the court of Napoleon III. His output comprising 12 operas, displays a marked variety with regard to either Italian or French operatic genres and styles on which he draws. The author defines: seven operas as belonging to the 'bel canto' type 'opera seria', one as a comic opera in the style of Italian 'opera buffa' . He further analyzes another opera, 'La contessina', attributing it to the 'semiseria' genre. Three other works are characterized as examples of French 'grand opéra' (Pierre de Médicis) and 'opéra comique' (Au travers du mur, L'Aventurier). The article ends with a conclusion that the composer was an international figure, and his musical idiom was not linked to Poland.