Isabella of Portugal (21 February 1397 – 17 December 1471) was Duchess of Burgundy as the third wife of Duke Philip the Good. Born a Portuguese infanta of the House of Aviz, Isabella was the only surviving daughter of King John I of Portugal and his wife Philippa of Lancaster. Her son by Philip was Charles the Bold, the last Valois Duke of Burgundy. Isabella was the regent of the Burgundian Low Countries during the absence of her spouse in 1432 and in 1441–1443. She served as her husband's representative in negotiations with England regarding trade relations in 1439 and those with the rebellious cities of Holland in 1444.