Humboldt, a Prussian at the court of King Charles IV of Spain

The study of Alejandro de Humboldt's transit through Spain and particularly Madrid, has been one of the forgotten aspects of his historiography. The r easons that would explain the approval by King Charles IV of his trip, invo lving minister Mariano de Urquijo and the ambassador of Sajonia, baron of F orell, are not sufficiently documented due to the scarce data that Humboldt himself offered in his work and to the absence of any other supporting doc uments. This work studies the preparation of his American trip and its appr oval by the Spanish court. It incorporates the Memorandum presented - which was "lost" until now -, the autobiography submitted to the authorities and the references given by Philippe de Forrell. Furthermore, it analyzes his relationships with the Spanish scientific community in Madrid and the profi le of the team that supported him to achieve his targets.