Bernal Díaz del Castillo (c. 1492 – 3 February 1584) was a Spanish conquistador who participated as a soldier in the conquest of the Aztec Empire under Hernán Cortés and late in his life wrote an account of the events.

In his later years, Castillo was an encomendero and governor in Guatemala where he wrote his memoirs called The True History of the Conquest of New Spain.

Castillo also took issue with the historical account published by the monk Bernardino de Sahagún, which he found to be overly sympathetic to the indigenous Americans, the Aztecs in particular.

[2] Though written decades after the events described, and containing numerous inaccuracies and biases, Castillo’s memoirs remain only one of two first-hand accounts of the Spanish overthrow of the Aztecs and are thus considered a valuable historical artifact.

[3][4] Attempting to explain the intentions and motivations of the Spaniards who arrived in Mexico, Castillo summarized it thus: "We came to serve God and to get rich, as all men wish to do.

Díaz served as a common foot soldier and hoped to make his fortune but when they reached Darien in present-day Colombia, they were quickly overcome by famine and an epidemic that killed more than half of the settlers.

Nevertheless, Díaz returned to the coast of Yucatán in April 1518, in an expedition led by Juan de Grijalva, with the intent of exploring the lands.

These accounts, and especially Díaz's own experiences, served as the basis for the recollections that Díaz later told with great drama to visitors and, eventually, a book entitled Historia verdadera de la conquista de la Nueva España (English: The True History of the Conquest of New Spain).

Bernal Díaz also examines the political rivalries of Spaniards, and gives accounts of the natives' human sacrifices, cannibalism and idolatry, which he claims he witnessed first-hand, as well as the artistic, cultural, political and intellectual achievements of the Aztecs, including their palaces, marketplaces and beautifully organized botanical and zoological gardens.

Similarly, the men's accounts provide extensive details about the actions of the Spaniards during their invasion of the Aztec Empire, creating controversy surrounding the aggression and force used by Cortés' army.

Historia verdadera de la conquista de la Nueva España, finished in 1568, almost fifty years after the events it described, was begun around the same time as his appointment as regidor and was well in progress by the mid-1550s when he wrote to the Holy Roman Emperor (and king of Spain), Charles V, describing his services and seeking benefits.

[7] Despite this, Castillo apparently was remorseful over the destruction of Tenochtitlan, writing in his History, "When I beheld the scenes around me, I thought within myself, this was the garden of the world.

[13] Alicia Mayer (2005) praised that edition, its selection, and León-Portilla's introduction, saying they remained, down to the date of her review, "fuente imprescindible de consulta" (an indispensable source to consult) without seeing his manuscript published.