Hernán Cortés enters Tenochtitlán and Aztec ruler Moctezuma welcomes him with a great celebration.

Hernán Cortés de Monroy y Pizarro Altamirano, 1st Marquis of the Valley of Oaxaca was a Spanish conquistador who led an expedition that caused the fall of the Aztec Empire and brought large portions of what is now mainland Mexico under the rule of the King of Castile in the early 16th century. Cortés was part of the generation of Spanish explorers and conquistadors who began the first phase of the Spanish colonization of the Americas.

Tenochtitlan, also known as Mexico-Tenochtitlan, was a large Mexican altepetl in what is now the historic center of Mexico City. The exact date of the founding of the city is unclear, but the date 13 March 1325 was chosen in 1925 to celebrate the 600th anniversary of the city. The city was built on an island in what was then Lake Texcoco in the Valley of Mexico. The city was the capital of the expanding Aztec Empire in the 15th century until it was captured by the Tlaxcaltec and the Spanish in 1521.

The Aztecs were a Mesoamerican civilization that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who dominated large parts of Mesoamerica from the 14th to the 16th centuries. Aztec culture was organized into city-states (altepetl), some of which joined to form alliances, political confederations, or empires. The Aztec Empire was a confederation of three city-states established in 1427: Tenochtitlan, the capital city of the Mexica or Tenochca, Tetzcoco, and Tlacopan, previously part of the Tepanec empire, whose dominant power was Azcapotzalco. Although the term Aztecs is often narrowly restricted to the Mexica of Tenochtitlan, it is also broadly used to refer to Nahua polities or peoples of central Mexico in the prehispanic era, as well as the Spanish colonial era (1521–1821). The definitions of Aztec and Aztecs have long been the topic of scholarly discussion ever since German scientist Alexander von Humboldt established its common usage in the early 19th century.