Philippa of Lancaster (Portuguese: Filipa [fiˈlipɐ]; 31 March 1360 – 19 July 1415) was Queen of Portugal from 1387 until 1415 as the wife of King John I.

Born into the royal family of England, her marriage secured the Treaty of Windsor and produced several children who became known as the "Illustrious Generation" in Portugal.

[5] Philippa married King John I by proxy, and in keeping with a unique Portuguese tradition, the stand-in bridegroom pretended to bed the bride.

[6] The marriage itself, as was usually the case for the nobility in the Middle Ages, was a matter of state and political alliance, and the couple did not meet until twelve days after they were legally married.

In one instance, Philippa intervened in court politics on "behalf of followers of the dethroned Richard II when they appealed for her help after her brother, Henry IV, had usurped the English throne".

[11] On another occasion, she persuaded the reluctant Earl of Arundel to marry her husband's illegitimate daughter Beatrice,[11] further cementing the alliance between Portugal and England.

[citation needed] Philippa presented her three eldest sons with jewel-encrusted swords, which they would use in their impending knighthoods, and gave each a portion of the True Cross, "enjoining them to preserve their faith and to fulfil the duties of their rank".

[13] At her death she prayed with several priests and, "without any toil or suffering, gave her soul into the hands of Him who created her, a smile appearing on her mouth as though she disdained the life of this world".

[12] Philippa was apparently a generous and loving queen, the mother of the "Illustrious Generation" (in Portuguese, Ínclita Geração) of infantes (princes) and infantas (princesses).

The medieval French poet Eustache Deschamps dedicated one of his ballads to "Phelippe en Lancastre," as a partisan of the Order of the Flower.