The Age of Discovery, or the Age of Exploration (approximately from the beginning of the 15th century until the middle of the 17th century), is an informal and loosely defined term for the period in European history in which extensive overseas exploration, led by the Portuguese, emerged as a powerful factor in European culture, most notably the European rediscovery of the Americas. It also marks an increased adoption of colonialism as a national policy in Europe. Several lands previously unknown to Europeans were discovered by them during this period, though most were already inhabited.

European exploration outside the Mediterranean started with the Portuguese discoveries of the Atlantic archipelagos of Madeira and Azores in 1419 and 1427 respectively, then the coast of West Africa after 1434 until the establishment of the sea route to India in 1498 by Vasco da Gama. The Crown of Castile (Spain) sponsored the transatlantic voyages of Christopher Columbus to the Americas between 1492 and 1504, and the first circumnavigation of the globe between 1519 and 1522 by the expedition of Ferdinand Magellan (completed by Juan Sebastián Elcano). These discoveries led to numerous naval expeditions across the Atlantic, Indian, and Pacific oceans, and land expeditions in the Americas, Asia, Africa, and Australia that continued into the late 19th century, followed by the exploration of the polar regions in the 20th century.

European overseas exploration led to the rise of global trade and the European colonial empires, with the contact between the Old World (Europe, Asia and Africa) and the New World (the Americas), as well as Australia, producing the Columbian exchange, a wide transfer of plants, animals, food, human populations (including slaves), communicable diseases and culture between the Eastern and Western Hemispheres. The Age of Discovery and later European exploration allowed the mapping of the world, resulting in a new worldview and distant civilisations coming into contact. At the same time, new diseases were propagated, decimating populations not previously in contact with the Old World, particularly concerning Native Americans. The era also saw the enslavement, exploitation, military conquest, and economic dominance and spread of European civilisation and superior technology by Europe and its colonies over native populations.