Henry, Cardinal-King of Portugal or Henrique  the Chaste (Portuguese o Casto) (Lisbon, 31 January 1512 – Almeirim, 31 January 1580) was the seventeenth King of Portugal and the Algarves. He ruled between 1578 and 1580.

Henry was the younger brother of King John III and, as a younger son, he was not expected to succeed to the Portuguese throne. Early in his life, Henry took Holy Orders to promote Portuguese interests within the Catholic Church, then dominated by Spain. He rose fast through the Church hierarchy, becoming in quick succession Archbishop of Braga, Archbishop of Évora and Grand Inquisitor before receiving a Cardinal's hat, receiving theTitulus Ss. Quattuor Coronatorum. Henry, more than anyone, endeavoured to bring the Jesuits to Portugal and employed them in the colonial empire.

He served as regent for his grand-nephew, king Sebastian I of Portugal, after 1557, and then succeeded him as king after the disastrous Battle of Alcácer-Quibir in 1578 in which Sebastian died. Henry renounced his clerical offices and sought to take a bride for the continuation of the Avis dynasty, but Pope Gregory XIII, affiliated with the Habsburgs, did not release him from his vows. The Cardinal-King died without having appointed a Council of Regency to choose a successor. One of the closest dynastic claimants was King Philip II of Spain who, in November 1580, sent the Duke of Alba to claim Portugal by force. Lisbon soon fell, and Philip was elected King of Portugal on condition that the kingdom and its overseas territories would not become Spanish provinces.