Portuguese succession crisis of 1580

As Sebastian and Henry lacked immediate heirs, a dynastic crisis unfolded, marked by internal conflicts and external contenders vying for the Portuguese throne.

Ultimately, Philip II of Spain succeeded Henry I as King of Portugal, uniting the Portuguese and Spanish Crowns in the Iberian Union.

[1][a] Henry renounced his clerical offices and sought to take a bride for the continuation of the Aviz dynasty, but Pope Gregory XIII, affiliated with Philip II, did not release him from his vows.

[3] In January 1580, when the Cortes were assembled in Almeirim to decide upon an heir, the Cardinal-King died and the Regency of the Kingdom was assumed by a Council of five members.

The heir by primogeniture was her nephew Ranuccio Farnese, being the son of Catherine's late older sister Maria,[7] followed by his siblings; then the Duchess herself and her children; and only after them, King Philip.

[9] The heir by primogeniture, 11-year-old Ranuccio Farnese, Hereditary Duke of Parma and Piacenza, was the grandson of Infante Duarte of Portugal,[10] the only son of Manuel I whose legitimate descendants survived at that time.

However, his father Alessandro Farnese, Duke of Parma was an ally of the Spanish king, another contender, so Ranuccio's rights were not claimed at that time.

Although she was Henry's preferred successor,[12] her bid for queenship ultimately failed due to her sex, the powerful influence of Philip II, and the unpopularity of her husband.

[7] According to primogeniture, the line of succession of the Portuguese throne would have been: Claimants following King Henry I's death (1580) Catherine de' Medici, Queen mother of France, used a claimed descendance from King Afonso III of Portugal from his first marriage with Matilda, Countess of Boulogne to advance with a claim to the Portuguese Throne.

John was raised to the throne of Portugal (of which he was then held to be the legitimate heir) during the Portuguese Restoration War against King Philip IV of Spain.