Diogo Cão (Portuguese pronunciation: [diˈoɣu ˈkɐ̃w̃]), anglicised as Diogo Cam and also known as Diego Cam, was a Portuguese explorer and one of the most notable navigators of the Age of Discovery. He made two voyages sailing along the west coast of Africa in the 1480s, exploring the Congo River and the coasts of the present-day Angola and Namibia.
Cão was born in Vila Real (some say in Évora), in the middle of the 15th century, the illegitimate son of Álvaro Fernandes or Gonçalves Cão, fidalgo of the Royal Household, himself the illegitimate son of Gonçalo Cão. He married and had four children: Pedro Cão, Manuel Cão, André Afonso Cão, and Isabel Cão.
He was the first European known to sight and enter the Congo River and to explore the West African coast between Cape St. Catherine in Gabon and Cape Cross, almost from the equator to Walvis Bay in Namibia.
When King John II of Portugal restarted the work of Henry the Navigator, he sent out Cão (probably around midsummer 1482) to explore the African coast south of the equator. He discovered the mouth and estuary of the Congo, probably in August 1482 and marked it with a padrão, or stone pillar erected on Shark Point, attesting to the sovereignty of Portugal. This padrão still stands to this day, albeit in ruins. He also ascended the great river for a short distance, and commenced modest commerce with the natives of the Bakongo kingdom. Cão then coasted down along the present Angola (Portuguese West Africa), and erected a second padrão, probably marking the termination of this voyage, at Cape Saint Mary (the Monte Negro of these first visitors). He returned to Lisbon by April 8, 1484, where John II ennobled him, promoting him from esquire to a knight of his household, and granted him an annuity and a coat of arms. On his return he discovered the Island of Annobón.
That Cão, on his second voyage of 1484–1486, was accompanied by Martin Behaim (as alleged on the latter's Nuremberg globe of 1492) is very doubtful. But it is known that the explorer revisited the Congo and erected two more padrão on land beyond his previous voyage. The first was at Cabo Negro, Angola, the second at Cape Cross. The Cape Cross pillar probably marked the end of his progress southward, some 1,400 kilometers. Cão ascended the Kongo River (which he thought led towards the realm of Prester John), up to the neighborhood of the site of Matadi. There, in October or November 1485, near the falls of Ielala, he left an inscription engraved on the stone which testifies of its passage and that of his men: Aqui chegaram os navios do esclarecido rei D.João II de Portugal - Diogo Cão, Pero Anes, Pero da Costa. ("Here reached the ships of the enlightned king John II of Portugal – Diogo Cão, Pero Anes, Pero da Costa").
According to one authority (a legend on the 1489 map of Henricus Martellus Germanus), Cão died off Cape Cross; but João de Barros and others wrote of his return to the Kongo, and subsequent taking of a native envoy to Portugal. The four pillars set up by Cão on his two voyages have all been discovered still on their original site, and the inscriptions on two of them from Cape Santa Maria and Cape Cross, dated 1482 and 1485 respectively, are still to be read and have been printed. The Cape Cross padrão is now at Berlin (replaced on the spot by a granite facsimile); those from the Kongo estuary and the more southerly Cape Santa Maria and Cabo Negro are in the Museum of the Lisbon Geographical Society.
Diogo Cão is the subject of Padrão, one of the best-known poems in Fernando Pessoa's book Mensagem, the only one published during the author's lifetime. He also figures strongly in the 1996 novel Lord of the Kongo by Peter Forbath.