Bernardino de Sahagún (1499-1590) was a Franciscan missionary to the Aztec (Nahua) people of Mexico, best known as the author of the Florentine Codex, also known as Historia general de las cosas de Nueva España (General History of the Things of New Spain).
In 1529 Sahagún was one of the first missionaries sent to New Spain, where he stayed for the remaining sixty years of his life. While converting and teaching the people of Tlaltelolco, near Mexico City, he learned to speak Náhuatl fluently, unlike most other missionaries, and began researching Aztec religion and culture. At the request of his superiors in the Franciscan order, he compiled his findings into Historia general de las cosas de Nueva España, an unparallelled work in Spanish and Náhuatl that took seven years to complete. Consisting of twelve books and a grammar and dictionary of Náhuatl, the Florentine Codex, as it is more commonly known, is one of the richest surviving sources of information on Aztec life before the conquest.
Miguel León-Portilla has called Sahagún "the first anthropologist", because his methods included using native informants to elicit information on Aztec culture from the Aztecs' point of view. He assembled three groups of Náhuatl tlatimines, or wise men, from different cities. He would ask questions, compare the answers of the three independent groups, and ask more questions to clarify the differences. All this was done in Náhuatl.
The book was not published immediately, however, because of Sahagun's criticism of the conquistadors and the fear that the book would inspire converted people to return to the religion of their ancestors. The manuscript was circulated within the Franciscan order and copied. It was published for the first time in Mexico in 1829.