Philippa of Lancaster

Philippa of Lancaster was Queen of Portugal from 1387 until her death in 1415 as the wife of King John I, founder of the House of Aviz. Her marriage cemented the Anglo-Portuguese alliance signed by the 1386 Treaty of Windsor, the oldest active diplomatic agreement still in force between two states.

Born in 1360 at Leicester Castle, she was the eldest surviving child of John of Gaunt, Duke of Lancaster, and his first wife Blanche of Lancaster. Through her father she was a granddaughter of Edward III of England and a half-sister of the future Henry IV. She received an unusually thorough education for a noblewoman of her generation, including instruction in Latin, theology, and English vernacular literature; her father's circle included Geoffrey Chaucer.

Her marriage to John I took place at Porto Cathedral in February 1387, sealing the political settlement that ended the 1383 to 1385 succession crisis with Castile. As queen she introduced English court customs, reformed royal household finances, and patronised religious foundations, including the Dominican monastery at Batalha that became the burial place of the Aviz dynasty.

She and John raised six surviving children later known to Portuguese historiography as the Ínclita Geração, the Illustrious Generation, including King Edward of Portugal, Prince Henry the Navigator, and the chronicler Peter, Duke of Coimbra. She died of plague at Sacavém in July 1415, days before the fleet she had blessed sailed for the Portuguese capture of Ceuta.

The forename Philippa is the feminine form of Philip, from the Greek Philippos, combining philos, meaning loving, with hippos, meaning horse, so the literal sense is "lover of horses." The name reached England through Norman aristocratic use, and her tomb effigy at Batalha alongside that of John I is one of the most-visited royal monuments in Portugal.