English: The six letters transcribed and translated here are very rare manuscripts: the only known texts in Old Tupi written by indigenous native speakers during the Brazilian colonial period. The manuscripts have been preserved for almost four hundred years in the Royal Library of The Hague, in the Netherlands. In this paper, they are completely transcribed, translated, and commented on for the first time, although their existence has been known since 1885. In 1630, the captaincy of Pernambuco, in Brazil, was invaded by the Dutch West Indies Company, and, subsequently, all of Brazil’s northeastern coast, except Bahia, was captured. After fifteen years of Dutch rule, the Portuguese began a war to retake their former northeastern possessions, in which the Potiguara Indians (‘prawn eaters’ < Old Tupi, potĩ – ‘prawn’ + ‘ûara – ‘one who eats’, ‘eater’) participated, some supporting the Catholic Portuguese and others supporting the Protestant Dutch. A few leading figures among the Potiguara, all from the same family and known to Portuguese and Brazilian historians as the Camarões (‘Prawns’), fought against each other during the conflict. At the beginning of hostilities, some of them exchanged letters between August and October 1645, and part of their correspondence was preserved in the Dutch archives.