In Modern scholarship, Renaissance Spain has been traditionally presented as marginal to the great cultural movement of the period called Humanism. One way to change this unjustified reputation and give a more accurate sense of the vibrant intellectual activity going on in the Spanish monarchy during the 16th and 17th century, is to look at the various networks of erudite correspondence exchanged between individuals in the different centers of learning of the Iberian Peninsula (cities, universities, the court) and the rest of Europe. Since letter writing has always been considered a defining attribute of Renaissance scholars, mapping out this Spanish Republic of Letters can help lay solid documentary foundations to this critical historiographical reassessment.