John of Reguengos

Infante John
Constable of Portugal Lord of Reguengos de Monsaraz, Colares and Belas
Detail from the St. Vincent Panels by Nuno Gonçalves, often believed to be a portrait of John of Reguengos, the Constable Prince.
Born	(1400-01-13)13 January 1400 Santarém, Kingdom of Portugal
Died	18 October 1442(1442-10-18) (aged 42) Alcácer do Sal, Kingdom of Portugal
Burial	Batalha Monastery
Spouse	Isabella of Barcelos
Issue details	Diogo, Constable of Portugal Isabella of Portugal, Queen of Castile Infanta Beatrice, Duchess of Viseu
House	House of Aviz
Father	John I of Portugal
Mother	Philippa of Lancaster
Religion	Roman Catholicism

Infante John, Constable of Portugal (Portuguese: João, Portuguese pronunciation: [ʒuˈɐ̃w̃]; 13 January 1400 – 18 October 1442) was a Portuguese infante (prince) of the House of Aviz, Constable of Portugal and master of the Portuguese Order of St. James (Santiago). In Portugal, he is commonly referred to as the O Infante Condestável ("the Constable Prince").

Infante John was the son of King John I of Portugal and his wife Philippa of Lancaster. John and his brothers Edward, Peter, Henry and Ferdinand, sister Isabella and half-brother Afonso, constitute what Portuguese historians have traditionally labelled the 'illustrious generation' (Ínclita Geração)

With his brothers, Infante John participated in the conquest of Ceuta (1415) and was knighted by his father in the aftermath. He was invested as the 1st Lord of Reguengos de Monsaraz, Colares and Belas shortly after. In October 1418, at the king's request, Pope Martin V approved the appointment of Infante John as the 10th Master of the Order of St. James of the Sword, bringing the old military order into the hands of the royal family. That same year (1418), John and his brother Henry the Navigator led a relief fleet to Ceuta and helped lift the Siege of Ceuta.