Henry the Navigator in the context of "Prester John"

The geography of North Africa has been reasonably well known among Europeans since classical antiquity in Greco-Roman geography. Northwest Africa (the Maghreb) was known as either Libya or Africa, while Egypt was considered part of Asia.

European exploration of sub-Saharan Africa begins with the Age of Discovery in the 15th century, pioneered by the Kingdom of Portugal under Henry the Navigator. The Cape of Good Hope was first reached by Bartolomeu Dias on 12 March 1488, opening the important sea route to India and the Far East, but European exploration of Africa itself remained very limited during the 16th and 17th centuries. The European powers were content to establish trading posts along the coast while they were actively exploring and colonizing the New World. Exploration of the interior of Africa was thus mostly left to the Muslim slave traders, who in tandem with the Muslim conquest of Sudan established far-reaching networks and supported the economy of a number of Sahelian kingdoms during the 15th to 18th centuries.

The Portuguese discovery of the sea route to India was the first recorded trip directly from Europe to the Indian subcontinent, via the Cape of Good Hope. Under the command of the Portuguese explorer Vasco da Gama, it was undertaken during the reign of King Manuel in 1497–1499. It is one of the most important events of the Age of Discovery and the Portuguese Empire, and it initiated the Portuguese maritime trade on the Malabar Coast and other parts of the Indian Ocean, the military presence and settlements of the Portuguese in Goa and Bombay.

Portuguese maritime explorations resulted in numerous territories and maritime routes recorded by the Portuguese on journeys during the 15th and 16th centuries. Portuguese sailors were at the vanguard of European exploration, chronicling and mapping the coasts of Africa and Asia, then known as the East Indies, Canada and Brazil (the West Indies), in what became known as the Age of Discovery.

Methodical expeditions started in 1419 along the coast of West Africa under the sponsorship of prince Henry the Navigator, whence Bartolomeu Dias reached the Cape of Good Hope and entered the Indian Ocean in 1488. Ten years later, in 1498, Vasco da Gama led the first fleet around Africa to the Indian subcontinent, arriving in Calicut and starting a maritime route from Portugal to India. Portuguese explorations then proceeded to southeast Asia, where they reached Japan in 1542, forty-four years after their first arrival in India. In 1500, the Portuguese nobleman Pedro Álvares Cabral became the first European to discover Brazil.

Río de Oro (Spanish: [ˈri.o ðe ˈoɾo] , Spanish for "River of Gold"; Arabic: وادي الذهب, Wādī-aḏ-Ḏāhab, often transliterated as Oued Edhahab) is the southern geographic region of Western Sahara. It was, with Saguia el-Hamra, one of the two territories that formed the Spanish province of Spanish Sahara after 1958; it had been taken as a Spanish colonial possession in the late 19th century. Its name seems to come from an east–west river which was supposed to have run through it. The river was thought to have largely dried out – a wadi, as the name indicates – or have disappeared underground.

The Spanish name is derived from its previous name Rio do Ouro, given to it by its Portuguese discoverer Afonso Gonçalves Baldaia in 1436. The Portuguese prince Henry the Navigator dispatched a mission in 1435, under Gil Eanes and Baldaia, to find the legendary River of Gold in western Africa. Going down the coast, they rounded the al-Dakhla peninsula in present-day Western Sahara and emerged into an inlet, which they excitedly believed to be the mouth of the River of Gold (see Senegal River). The name continued to be used for the inlet and the surrounding area although no gold was found there, neither in the water of the narrow gulf, probably mistaken for the river itself, nor in its neighborhood. Some gold dust, however, was obtained from the natives.

Afonso Gonçalves Baldaia was a 15th-century Portuguese nautical explorer. He explored much of the coast of Western Sahara in 1435–1436 on behalf of the Portuguese prince Henry the Navigator. He would later become one of the first colonists of Terceira Island in the Azores.