Between 1519 and 1526, Hernán Cortés sent five letters to the Emperor Charles V. These letters contain details of his explorations and conquests, as well as information about Aztec culture and society. Although they were addressed personally to the Emperor, the letters were clearly intended for public consumption, and all but the fifth were published during Cortés's lifetime. They remain important primary sources for historians, particularly the third letter, which contains a map of the Aztec capital, Tenochtitlán.

There is no evidence that the letters had any influence on Spanish exploration policy or on the treatment of Native Americans by Europeans. Indeed, it is difficult to see how they could have been particularly influential in the latter case, since the Europeans who went to America were necessarily influenced primarily by circumstances and their own ideas about the people they encountered. It is possible that the descriptions of a relatively sophisticated society may have given rise to a more enlightened view of Native Americans in Europe, but it is certainly not clear that affected their treatment in the Americas.

Neither of these objectives seem to have been important to Cortés, who was far more interested in advancing his own career and denigrating his enemies—in particular, the Governor of Cuba, Diego Velázquez. In the first object, they apparently succeeded, since Cortés was treated with great honor and created Marquess of the Valley of Oaxaca when he returned to Spain in 1528.