Conquistadors (also spelled Conquistadores, as in Portuguese or Spanish)(/k?n?k(w)?st?d??r/, also US: /-?ki?s-, k???-/, Spanish: [ko?kista?ðo?], Portuguese: [k?ki?t??do?, kõki?t??ðo?]; Portuguese and Spanish for "conqueror") were the knights, soldiers and explorers in service of the Spanish Empire and the Portuguese Empire. The preeminence of the Iberian kingdoms of Portugal and Spain during the Age of Discovery resulted in the large numbers of conquistadors that sailed from Europe to the Americas, Africa, Asia, and Oceania, conquering territory and opening trade routes, in the 15th, 16th, 17th, and 18th centuries.

Conquistadors in the service of the Spanish Crown led the conquests of numerous territories for the Spanish Empire, across North America, the Caribbean, and South America, founding the basis for modern Hispanic America. Notable Spanish conquistadors include Hernán Cortés (who led the Conquest of Mexico), Francisco Pizarro (who led the Conquest of Peru), and Hernando de Soto (who was led the first European expedition into the modern United States).

Conquistadors in the service of the Portuguese Crown led numerous conquests for the Portuguese Empire, across South America, Africa, Asia, the Middle East, and Oceania, 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), Ferdinand Magellan (who led the first circumnavigation of the world), and Filipe de Brito e Nicote (who led conquests into Burma and was made King of Pegu).