The project of finding the Senegal was taken up in the 1420s by the Portuguese Prince Henry the Navigator, who invested heavily to reach it. In 1434, one of Henry's captains, Gil Eanes, finally surpassed Cape Bojador and returned to tell about it. Henry immediately dispatched a follow up mission in 1435, under Gil Eanes and Afonso Gonçalves Baldaia. Going down the coast, they turned around the al-Dakhla peninsula in the Western Sahara and emerged into an inlet, which they excitedly believed to be the mouth of the Senegal River. The name they mistakenly bestowed upon the inlet - "Rio do Ouro" - is a name it would remain stuck with down to the 20th century.
Realizing the mistake, Henry kept pressing his captains further down the coast, and in 1445, the Portuguese captain Nuno Tristão finally reached the Langue de Barbarie, where he noticed the desert end and the treeline begin, and the population change from 'tawny' Sanhaja Berbers to 'black' Wolof people. Bad weather or lack of supplies prevented Tristão from actually reaching the mouth of the Senegal River, but he rushed back to Portugal to report he had finally found the "Land of the Blacks" (Terra dos Negros), and that the "Nile" was surely nearby. Shortly after (possibly still within that same year) another captain, Dinis Dias (sometimes given as Dinis Fernandes) was the first known European since antiquity to finally reach the mouth of the Senegal River. However, Dias did not sail upriver, but instead kept sailing down the Grande Côte to the bay of Dakar.
The very next year, in 1446, the Portuguese slave-raiding fleet of Lançarote de Freitas arrived at the mouth of the Senegal. One of its captains, Estêvão Afonso, volunteered to take a launch to explore upriver for settlements, thus becoming the first European to actually enter the Senegal river. He didn't get very far. Venturing ashore at one point along the river bank, Afonso tried to kidnap two Wolof children from a woodsman's hut. But he ran into their father, who proceeded to chase the Portuguese back to their launch and gave them such a beating that the explorers gave up on going any further, and turned back to the waiting caravels.
Sometime between 1448 and 1455, the Portuguese captain Lourenço Dias opened regular trade contact on the Senegal River, with the Wolof statelets of Waalo (near the mouth of the Senegal River) and Cayor (a little below that), drumming up a profitable business exchanging Mediterranean goods (notably, horses) for gold and slaves. Chronicler Gomes Eanes de Zurara, writing in 1453, still called it the "Nile River", but Alvise Cadamosto, writing in the 1460s, was already calling it the "Senega" [sic], and it is denoted as Rio do Çanagà on most subsequent Portuguese maps of the age. Cadamosto relates the legend that both the Senegal and the Egyptian Nile were branches of the Biblical Gihon River that stems from the Garden of Eden and flows through Ethiopia. He also notes that the Senegal was called "the Niger" by the ancients - probably a reference to Ptolemy's legendary 'Nigir' (below the Gir), which would be later identified by Leo Africanus with the modern Niger River. Much the same story is repeated by Marmol in 1573, with the additional note that both the Senegal River and Gambia River were tributaries of the Niger River. However, the contemporary African atlas of Venetian cartographer Livio Sanuto, published in 1588, sketches the Senegal, the Niger and the Gambia as three separate, parallel rivers.
Senegambia region, detail from the map of Guillaume Delisle (1707), which still assumes the Senegal connected to the Niger; this would be corrected in subsequent edititions of Delisle's map (1722, 1727), where it was shown ending at a lake, south of the Niger.Portuguese chronicler João de Barros (writing in 1552) says the river's original local Wolof name was Ovedech (which according to one source, comes from "vi-dekh", Wolof for "this river"). His contemporary, Damião de Góis (1567) records it as Sonedech (from "sunu dekh", Wolof for "our river"). Writing in 1573, the Spanish geographer Luis del Marmol Carvajal asserts that the Portuguese called it Zenega, the 'Zeneges' (Berber Zenaga) called it the Zenedec, the 'Gelofes' (Wolofs) call it Dengueh, the 'Tucorones' (Fula Toucouleur) called it Mayo, the 'Çaragoles' (Soninke Sarakole of Ngalam) called it Colle and further along (again, Marmol assuming Senegal was connected to the Niger), the people of Bagamo' (Bambara of Bamako?) called it Zimbala (Jimbala?) and the people of Timbuktu called it the Yça