João I
King of Portugal and the Algarve
Reign	April 6, 1385—August 14, 1433 (Regent and Defender of the Kingdom since December 6, 1383)
Full name	João of Portugal
Titles	Grand Master of the Order of Aviz (1364–1387) Regent and Defender of the Kingdom (1388–1385) Lord of Ceuta (1415–1433)
Born	April 11, 1357
Birthplace	Lisbon, Kingdom of Portugal
Died	August 13, 1433 (aged 76)
Place of death	Lisbon, Kingdom of Portugal
Buried	Chapel of the Founder, Monastery of Batalha, Batalha, District of Leiria, Portugal
Predecessor	Ferdinand I of Portugal Beatrice of Portugal (disputed)
Heir daughter first son second son	Infanta Branca (1388–1389) Infante Afonso (1390) Infante Duarte (future Edward I) (1391–1433)
Successor	Edward of Portugal
Consort	Philippa of Lancaster
Offspring	Infanta Branca (1388–1389) Infante Afonso (1390) Infante Duarte (future Edward I) (1391–1438) Infante Pedro, Duke of Coimbra (1392–1449) Infante Henrique, Duke of Viseu (Henry the Navigator) (1394–1460) Infanta Isabel, Duchess of Burgundy (1397–1471) Infanta Branca (1398) Infante João (1400–1442) Infante Fernando, the Saint Prince (1402–1443) Afonso, 1st Duke of Braganza (c. 1380–1461; natural son) Beatriz, Countess of Arundel and Huntingdon (c. 1382–1439; natural daughter)
Royal House	House of Aviz
Dynasty	Dynasty of Aviz (Joanine Dynasty)
Father	Peter I of Portugal
Mother	Teresa Gille Lourenço

Portuguese royalty
House of Avis

John I Children    Infante Duarte (future Edward I)    Infante Pedro, Duke of Coimbra    Henry the Navigator (Infante Henrique, Duke of Viseu)    Infanta Isabel, Duchess of Burgundy    Infante João, Lord of Reguengos    Infante Fernando, the Saint Prince    Afonso, Duke of Braganza (illegitimate)    Beatriz, Countess of Arundel (illegitimate) Grandchildren include    Infanta Isabel of Coimbra, Queen of Portugal Edward Children    Afonso, Prince of Portugal (future Afonso V)    Infante Fernando, Duke of Viseu    Infanta Leonor, Holy Roman Empress    Infanta Catarina    Infanta Joana, Queen of Castile Grandchildren include    Infante Manuel, Duke of Beja (future Manuel I)    Infanta Leonor of Viseu, Queen of Portugal Great-Grandchildren include    Jaime, Duke of Braganza, Prince of Portugal Afonso V Children include    João, Prince of Portugal    Blessed Joana, Princess of Portugal    João, Prince of Portugal (future John II) John II    Afonso, Prince of Portugal    Jorge, Duke of Coimbra (illegitimate)

Joao I (Portugues: João, pronounced [ʒuˈɐ̃ũ]; Lisbon, 11 April 1357 – Lisbon, 14 August 1433), called the Good (sometimes the Great) or of Happy Memory, was the tenth King of Portugal and the Algarve and the first to use the title Lord of Ceuta. He was the natural son of Pedro I by a noble Galician woman named Teresa Lourenço, daughter of Lourenço Martins, o da Praça, and wife Sancha Martins. In 1364 he was created grand-master of the Order of Aviz. He became king in 1385, after the 1383–1385 Crisis.

On the death of his lawful brother Fernando I in October 1383, without a male heir, strenuous efforts were made to secure the succession for princess Beatrice, his only daughter. As heiress-apparent Beatrice had been married to king Juan I of Castile, but the popular voice declared against an arrangement by which Portugal would virtually have become united with Castile. The 1383–1385 Crisis followed as a period of political anarchy, when no king ruled the country.

On April 6, 1385, the council of the kingdom (cortes in Portuguese) met in Coimbra and declared João, then Master of Aviz, king of Portugal. This was in effect a declaration of war against Castile and its claims to the Portuguese throne. Soon after, the king of Castile invaded Portugal, with the purpose of conquering Lisbon and removing João I from the throne. Juan I was accompanied by French allied cavalry as English troops and generals took the side of João (see Hundred years war). João I then named Nuno Álvares Pereira, his loyal and talented supporter, general and protector of the Kingdom. The invasion was repelled during the Summer after the Battle of Atoleiros, but especially after the decisive battle of Aljubarrota (August 14, 1385), where the Castilian army was virtually annihilated. Juan I of Castile then retreated and the stability of João I's throne was permanently secured.

On 11 February 1387, João I married Philippa of Lancaster, daughter of John of Gaunt who had proved to be a worthy ally, consolidating the union of the Anglo-Portuguese Alliance that endures to the present day.

After the death of Juan of Castile in 1390, without leaving issue by Beatrice, João I ruled in peace and pursued the economic development of the country. The only significant military action was the siege and conquest of the city of Ceuta in 1415. By this step he aimed to control navigation of the African coast. But in longer perspective, this was the first step opening the Arabian world to medieval Europe, which in fact led to the Age of Discovery with Portuguese explorers sailing across the whole world. It should be noted that the global Muslim population had climbed to about 8 per cent as against the Christian population of 14 per cent by 1400.

Contemporaneous writers describe him as a man of wit, very keen on concentrating the power on himself, but at the same time with a benevolent and kind personality. His youth education as master of a religious order made him an unusually learned king in the Middle Ages. His love for knowledge and culture was passed to his sons: Duarte, the future king, was a poet and a writer, Pedro, the duke of Coimbra, was one of the most learned princes of his time and Prince Henry the Navigator, the duke of Viseu, started a school of navigation and invested heavily in science and development of nautical topics. In 1430, his only surviving daughter, Isabella, married Philip the Good, Duke of Burgundy and enjoyed an extremely refined court in his lands; she was the mother of Charles the Bold.

Genealogical data

Ancestors

Marriages and descendants

João I married at Oporto on February 2, 1387 Philippa of Lancaster, daughter of John of Gaunt, 1st Duke of Lancaster and Blanche of Lancaster. From that marriage were born several famous princes and princesses of Portugal (Infantes) that became known as the Illustrious Generation (Portuguese: Ínclita Geração).

This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.

Sources:

Williamson, D. 1988. ‘’Debrett’s Kings and Queens of Europe’’