Philippa of Lancaster (1359 - July 19, 1415) was an English princess, daughter of John of Gaunt, duke of Lancaster by his wife and cousin Blanche of Lancaster (daughter of Henry of Lancaster).

Philippa became queen consort of Portugal by her marriage with king John I, celebrated in 1387 in the city of Porto. This marriage was the final step in the Portuguese-English alliance, against the France-Castile axis. Philippa is remembered for being a generous and loving queen, and by being the mother of the "Illustrious Generation" (in Portuguese, Ínclita Geração) of princes. Their children were refined and respected princes all over Europe. Edward, king of Portugal, was a writer and an intellectual; Peter, Duke of Coimbra was a remarkable ruler and a traveled man; Henry, the Navigator, guided Portugal to the Great era of The Discoveries; Isabella, duchess of Burgundy, was one of the most powerful and admired women in Europe; John was also a very respected noble, and he was the grandfather of the two greatest Iberian monarchs in the 16th century; Ferdinand, the Saint Prince, a warrior, was captured during the Disaster of Tanger and died prisoner of the Moors. Philippa died of plague in 1415, a few days before the expedition to Ceuta.