Hernn Corts de Monroy y Pizarro Altamirano, 1st Marquess of the Valley of Oaxaca (; Spanish: [ena kotez e monroj i piaro altamiano]; 1485 December 2, 1547) 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. Corts was part of the generation of Spanish explorers and conquistadors who began the first phase of the Spanish colonization of the Americas.

Born in Medelln, Spain, to a family of lesser nobility, Corts chose to pursue adventure and riches in the New World. He went to Hispaniola and later to Cuba, where he received an encomienda (the right to the labor of certain subjects). For a short time, he served as alcalde (magistrate) of the second Spanish town founded on the island. In 1519, he was elected captain of the third expedition to the mainland, which he partly funded. His enmity with the Governor of Cuba, Diego Velzquez de Cullar, resulted in the recall of the expedition at the last moment, an order which Corts ignored.

Arriving on the continent, Corts executed a successful strategy of allying with some indigenous people against others. He also used a native woman, Doa Marina, as an interpreter. She later bore his first son. When the Governor of Cuba sent emissaries to arrest Corts, he fought them and won, using the extra troops as reinforcements. Corts wrote letters directly to the king asking to be acknowledged for his successes instead of being punished for mutiny. After he overthrew the Aztec Empire, Corts was awarded the title of Marqus del Valle de Oaxaca, while the more prestigious title of Viceroy was given to a high-ranking nobleman, Antonio de Mendoza. In 1541 Corts returned to Spain, where he died six years later of natural causes.

Conquistadors (, US also ) or conquistadores (Spanish: [koŋkistaˈðoɾes], Portuguese: [kũkiʃtɐˈdoɾis, kõkiʃtɐˈðoɾɨʃ]; meaning 'conquerors') were the explorer-soldiers of the Spanish and Portuguese Empires of the 15th and 16th Centuries. During the Age of Discovery, conquistadors sailed beyond Europe to the Americas, Oceania, Africa, and Asia, colonizing and opening trade routes. They brought much of the Americas under the dominion of Spain and Portugal.

After arrival in the West Indies in 1492, the Spanish, usually led by hidalgos from the west and south of Spain, began building an American empire in the Caribbean using islands such as Hispaniola, Cuba, and Puerto Rico as bases. From 1519 to 1521, Hernán Cortés waged a campaign against the Aztec Empire, ruled by Moctezuma II. From the territories of the Aztec Empire, conquistadors expanded Spanish rule to northern Central America and parts of what is now the southern and western United States, and from Mexico sailing the Pacific Ocean to the Philippines. Other conquistadors took over the Inca Empire after crossing the Isthmus of Panama and sailing the Pacific to northern Peru. As Francisco Pizarro subdued the empire in a manner similar to Cortés other conquistadores used Peru as base for conquering much of Ecuador and Chile. Central Colombia, home of the Muisca was conquered by licentiate Gonzalo Jiménez de Quesada, and its northern regions were explored by Rodrigo de Bastidas, Alonso de Ojeda, Juan de la Cosa, Pedro de Heredia and others. For South Western Colombia, Bolivia, and Argentina, conquistadors from Peru combined parties with other conquistadors arriving more directly from the Caribbean and Río de la Plata-Paraguay respectively. All these conquests founded the basis for modern Hispanic America and the Hispanophone.

Spanish conquistadors also made significant explorations into the Amazon Jungle, Patagonia, the interior of North America, and the discovery and exploration of the Pacific Ocean. Conquistadors founded numerous cities, some of them on locations with pre-existing settlements, Manila and Mexico City.

Conquistadors in the service of the Portuguese Crown led numerous conquests for the Portuguese Empire, across South America and Africa, as well as commercial colonies in Asia, founding the origins of modern Portuguese-speaking world in the Americas, Africa, and Asia. Notable Portuguese conquistadors include Afonso de Albuquerque who led conquests across India, the Persian Gulf, the East Indies, and East Africa, and Filipe de Brito e Nicote who led conquests into Burma and was made King of Pegu.