Luiz Vicente De Simoni (1782-1881) was an Italian physician who went to Rio de Janeiro in 1817, and was constantly involved in the musical and theatrical scene of the city. He is the author of Marilia de Itamaraca (1854, music by Adolpho Maersch), considered by some authors as the first "Brazilian" opera. The subject is historical and narrates some episodes of the 17th century war against the Dutch. One of his main concerns was the use of Brazilian and Portuguese themes in operas, in order to invent something "national". As part of a broader movement, the idea was to explore Brazilian people, landscape and traditions as the main subject for operas that should be sung in Portuguese. The movement was related to a broader political project sponsored by the government and the Emperor, aimed at the revision of Brazilian history and the construction of a new cultural identity for the country. The purpose of this paper is to examine some aspects of the libretto of Marilia de Itamaraca and the ideas discussed in its preface, showing the contradictions and tensions involved in the creation of a "national" identity through operas.2039113135