||This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. (April 2012)|
|Portrait of the King Dom John I; c. 1435|
|Reign||6 April 1385 – 14 August 1433|
|Spouse||Philippa of Lancaster|
|Edward, King of Portugal
Peter, Duke of Coimbra
Henry the Navigator
Infanta Isabella, Duchess of Burgundy
John, Lord of Reguengos de Monsaraz
Fernando, the Saint Prince
Afonso, 1st Duke of Braganza (natural son)
Beatrice, Countess of Arundel (natural daughter)
|House||House of Aviz|
|Father||Peter I of Portugal|
|Born||11 April 1358
Lisbon, Kingdom of Portugal
|Died||14 August 1433
Lisbon, Kingdom of Portugal
|Burial||Chapel of the Founder, Monastery of Batalha, Batalha, District of Leiria, Portugal|
John I KG (Portuguese: João I [ʒuˈɐ̃w̃]; 11 April 1358 – 14 August 1433) was King of Portugal and the Algarve in 1385–1433. He was called the Good (sometimes the Great) or of Happy Memory, more rarely and outside Portugal, in Spain, the Bastard, and was the first to use the title Lord of Ceuta.
Early life 
John was born in Lisbon as the natural son of Peter I by a woman named Teresa, who, according to Fernão Lopes, was a noble Galician. In the eighteenth century, António Caetano de Sousa found a document on Torre do Tombo, of the sixteenth century, where she was named Teresa Lourenço. In 1364, by request of D. Nuno Freire de Andrade, a Galician Grand Master of the Order of Christ, he was created Grand Master of the Order of Aviz, by which title he was known. He became king in 1385, after the 1383–1385 Crisis.
On the death of his half-brother Ferdinand I without a male heir in October 1383, strenuous efforts were made to secure the succession for Princess Beatrice, Ferdinand's only daughter. As heiress presumptive, Beatrice had married king John I of Castile, but popular sentiment was against an arrangement in which Portugal would have become virtually annexed by Castile. The 1383–1385 Crisis followed, a period of political anarchy, when no monarch ruled the country.
On 6 April 1385, the Council of the Kingdom (the Portuguese Cortes) met in Coimbra and declared John, then Master of Aviz, King of Portugal. This was followed by the liberation of almost all of the Minho in only two months, on the war against Castile and its claims to the Portuguese throne. Soon after, the King of Castile again invaded Portugal with the purpose of conquering Lisbon and removing John I from the throne. John I of Castile was accompanied by French allied cavalry while English troops and generals took the side of John (see Hundred Years' War). John I and Nuno Álvares Pereira, his loyal Constable and talented supporter, repelled the attack on the decisive Battle of Aljubarrota (14 August 1385), where the Castilian army was virtually annihilated. John I of Castile then retreated. The Castilian forces abandoned Santarém, Torres Vedras, Torres Novas, many other towns were delivered to John I by Portuguese nobles from the Castilian side and the stability of the Portuguese throne was permanently secured.
After the death of John I of Castile in 1390, without leaving issue by Beatrice, John I of Portugal 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 the broader 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.
Contemporaneous writers describe John as a man of wit, very keen on concentrating power on himself, but at the same time with a benevolent and kind personality. His youthful education as master of a religious order made him an unusually learned king for the Middle Ages. His love for knowledge and culture was passed to his sons, often collectively referred to by Portuguese historians as the "illustrious generation" (Ínclita Geração): Edward, the future king, was a poet and a writer; Peter, the Duke of Coimbra, was one of the most learned princes of his time; and Prince Henry the Navigator, the duke of Viseu, invested heavily in science and the development of nautical pursuits. In 1430, John's only surviving daughter, Isabella, married Philip the Good, Duke of Burgundy, and enjoyed an extremely refined court culture in his lands; she was the mother of Charles the Bold.
Marriages and descendants 
John I married in Porto on 2 February 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).
|By Philippa of Lancaster (1359– 19 July 1415; married on 2 February 1387)|
|Infanta Blanche||13 July 1388||6 March 1389|
|Infante Afonso||30 July 1390||22 December 1400|
|King Edward||31 October 1391||13 September 1438||Who succeeded him as King of Portugal.|
|Infante Peter||9 December 1392||20 May 1449||Duke of Coimbra. Died in the Battle of Alfarrobeira.|
|Infante Henry||4 March 1394||13 November 1460||Known as Henry the Navigator. Duke of Viseu and Grand-Master of the Order of Christ.|
|Infanta Isabella||21 February 1397||11 December 1471||Duchess Consort of Burgundy by marriage to Philip III, Duke of Burgundy.|
|Infanta Blanche||11 April 1398||27 July 1398|
|Infante John||13 January 1400||18 October 1442||Constable of the Kingdom and grandfather of Isabella I of Castile.|
|Infante Ferdinand||29 September 1402||5 June 1443||Grand Master of the Order of Aviz. Died in captivity in Fes, Morocco.|
|By Inês Peres (c. 1350–1400?)|
|Afonso||10 August 1377||15 December 1461||Natural son and 1st Duke of Braganza.|
|Beatrice||c. 1382||25 October 1439||Natural daughter. Countess of Arundel by marriage to Thomas Fitzalan, 12th Earl of Arundel. Countess of Huntingdon by marriage to John Holland, 2nd Earl of Huntingdon, later Duke of Exeter.|
|Ancestors of John I of Portugal|
- Williamson, D. 1988. ‘’Debrett’s Kings and Queens of Europe’’
- ANA ECHEVARRÍA ARSUAGA: "CATALINA DE LANCASTER", edit. Nerea, 2002. ISBN 84-89569-79-7). Graduated at the University of madrid and a dr. at the University of Edinburgh, England, she teaches med¡ieval history at the UNED University, Spain.
John I of Portugal
Cadet branch of the Portuguese House of BurgundyBorn: 11 April 1358 Died: 14 August 1433
|King of Portugal and the Algarve