Henry the Navigator
The third son of Portuguese King John I, the Infante Henrique, Duke of Viseu (1394 – 1460), better known as Henry the Navigator (Henrique, o Navegador), is widely regarded as the initiator of the Age of Discovery due to his role in the early development of Portuguese exploration and maritime trade through the systematic exploration of Western Africa, the islands of the Atlantic Ocean, and the search for a sea route around Africa that would bring the Portuguese into contact with the Indies and potential allies in the ongoing struggle against Islam.
Despite the historiographical legend, he made no more than two or three short sea trips between the Iberian peninsula and Morocco, where a disastrous military campaign in 1437 saw Henry leave his younger brother Ferdinand as a hostage while Henry extricated the Portuguese army. When the Portuguese Cortes refused to approve the ransom for the Infante Ferdinand, he remained in captivity until his death six years later.
Unable to embark on exploratory voyages himself, he entrusted the task to members of his household. Still, Henry (or, more accurately, his underlings) made two genuine contributions.
One involved the Volta do Mar ("turn of the sea") navigation triangle linking the Portuguese seaboard with West Africa, Madeira and the Azores.
The second was an extension of European knowledge of Africa's coast that set the scene for the later exploration in the 1470s and 1480s.
See here for a more detailed biographical sketch.
