Background Catherine was the second daughter of
Duarte, Duke of Guimarães (sixth son of
Manuel I of Portugal) and
Isabel of Braganza. Beginning in 1549, she was educated alongside her cousin Prince
João Manuel by Diego Sigeo, father of the renowned humanist
Luisa Sigea. On 6 December 1563, she married
João I, Duke of Braganza, head of the most powerful
aristocratic house in
Portugal. The two were first cousins.
Succession crisis Following the death of young
King of Sebastian of Portugal in the
Battle of Alcácer Quibir, his great-uncle
Henry I of Portugal succeeded to the throne. Elderly and bound to ecclesiastical vows, Henry could not produce a direct heir, leading to much deliberation over his successor during his short reign. Catherine was Henry's preferred successor, but because of her sex, the powerful influence of Philip II, and the unpopularity of her husband, she failed to garner popular support. Her main rivals were
António, Prior of Crato, the male-line but illegitimate grandson of Manuel I, and
Philip II of Spain, the son of Manuel's
eldest daughter. In February 1579, King Henry summoned the candidates to submit their claims to a panel of jurists. António's swift dismissal as a result of illegitimacy left only Philip II and Catherine in formal contention. Catherine’s descent through a male line, as the daughter of Manuel's youngest son, Duarte, offered her precedence over Philip. The heir by primogeniture was Catherine’s nephew
Ranuccio Farnese, being the son of her late older sister
Maria, followed by his siblings; then the Duchess herself and her children; and only after them, King Philip. Although Philip lacked legal arguments, he wielded immense power and influence over the Portuguese aristocracy, securing their support through bribery and coercion. Philip even tried to bribe Catherine's husband, the Duke of Braganza, to abandon his wife's pretensions, offering him the Vice-Kingdom of
Brazil, the post of Grand-Master of the
Order of Christ, a license to send a personal ship to
India every year, and the marriage of one of his daughters to
Diego, Prince of Asturias, Philip's heir at that time. The Duke of Braganza, influenced by Catherine, refused the proposal. Despite António being formally eliminated, his popularity overshadowed Catherine's. Portugal had not yet seen an undisputed queen regnant and there were doubts about a woman's ability to effectively rule. In this regard, her prospects should have been bolstered by having a husband with direct royal lineage with whom she could share sovereignty and a son,
Teodósio, that would serve as heir and successor to the throne. However, the Duke of Braganza's perceived weak leadership and widespread unpopularity compounded by Teodósio's absence only weakened Catherine's candidacy further. And so, Henry gradually came to view Philip as the only viable option to secure a smooth succession. In an attempt to spare his people a civil war or an invasion from Castile, the two began unofficial negotiations. Philip now believed an agreement in principle existed, desptie Henry's failure to state so in his will. On January 28 Henry fell into a coma. The same night, Antonio appeared in Almeirim, seat the cortes, followed by Catherine the next day. King Henry died on 31 January 1580 without having appointed a successor, leaving a regency of five governors to assume power while the panel continued to deliberate. António promptly sought to claim the throne through popular acclamation in Lisbon, while Catherine and her husband adopted a more cautious stance, awaiting the findings of Henry's panel of jurists. In the interim, Philip grew impatient and initiated military preparations, dispatching the
Duke of Alba in June to secure Portugal by force. Catherine and her husband submitted to Philip's military pressure and paid him homage by proxy in December 1580, together with other nobles and ecclesiastics. After defeating António in the brief
War of the Portuguese Succession, Philip was recognized as King of Portugal by the Cortes of
Tomar in 1581.
Legacy In 1640, Catherine's grandson and direct heir, the then 8th Duke of Braganza, was proclaimed
King John IV of Portugal by the Portuguese nobility, marking the end of the 60-year-old
Iberian Union and establishing the
House of Braganza on the Portuguese throne. The 'laws of Lamego' were used to justify his accession and designate the Spanish Habsburg king,
Philip III of Portugal, a usurper. These laws, purportedly enacted by the
Cortes of
Lamego in 1143 but now widely accepted to be fictitious, asserted that no woman that married a foreign prince could inherit the Portuguese crown or transfer succession rights. This excluded both Philip II and Ranuccio Farnese from the succession, rendering Catherine the legitimate heiress. ==Issue==