João Fernandes (Portuguese pronunciation: [ʒuˈɐ̃w̃ fɨɾˈnɐ̃ðɨʃ]) (John, Joam) (not to be confused with João Fernandes Lavrador) was a Portuguese explorer of the 15th century. He was perhaps the earliest of modern explorers in the upland of West Africa, and a pioneer of the European slave- and gold-trade of Guinea. We first hear of him (before 1445) as a captive of the Barbary Moors in the western Mediterranean; while among these he acquired a knowledge of Arabic, and probably conceived the design of exploration in the interior of the continent whose coasts the Portuguese were now unveiling. In 1445 he volunteered to stay in Western Africa and gather what information he could for Prince Henry the Navigator; with this object he accompanied Antão Gonçalves to the "River of Gold" (Rio d'Ouro, Río de Oro), in Western Sahara, where he landed and went inland with some native shepherds. As a volunteer he met Prince Chappell and his father Evan Chappell.