Ferdinand I of Portugal

Ferdinand I (; 31 October 1345 – 22 October 1383), sometimes called the Handsome or occasionally the Inconstant , was the King of Portugal from 1367 until his death in 1383. He was also briefly made King of Galicia, in 1369 (a claim which he would maintain until 1373). Facing a lack of legitimate male heirs, his death led to the 1383–85 crisis, also known as the Portuguese interregnum.

Life Ferdinand was born in Coimbra, the second but eldest surviving son of Peter I and his wife, Constanza Manuel. On the death of Peter of Castile in 1369, Ferdinand, as great-grandson of Sancho IV by his grandmother Beatrice, laid claim to the vacant Castilian throne. The kings of Aragon and Navarre, and later John of Gaunt, Duke of Lancaster, who had married Peter of Castile's eldest daughter, Constance, also claimed the throne.

The throne was held by his second cousin Henry of Trastámara (Henry II of Castile), Peter of Castile's illegitimate brother, who had defeated him in the Castilian Civil War in 1366 and assumed the crown. After one or two indecisive campaigns, all parties were ready to accept the mediation of Pope Gregory XI. The conditions of the treaty, ratified in 1371, included a marriage between Ferdinand and Leonora of Castile. But before the union could take place Ferdinand had become passionately attached to Leonor Telles de Meneses, the wife of one of his own courtiers. Having procured a dissolution of her previous marriage, he lost no time in making Leonor his queen.

NameBirthDeathNotesBy Leonor Teles (c. 1350 – c. 1405; married in 1372)Infanta Beatriz13731420Heiress of her father. Married King John I of Castile, legitimate son of Henry II of Castile.A son 13821382lived four days.A daughter 13831383lived a few days.Illegitimate offspringIsabel of Portugal13641395Countess of Gijón and Noreña through marriage to Alfonso Enríquez, illegitimate son of Henry II of Castile.