Dom (honorific) in the context of "João de Castro"

Dom John IV (João; 19 March 1604 – 6 November 1656), also known by the Portuguese as John the Restorer (João, o Restaurador), was the King of Portugal from 1640 until his death in 1656. He restored the independence of Portugal from Habsburg Spanish rule by terminating the 60-year-old Iberian Union in which Portugal and Spain shared the same monarch, and by establishing the House of Braganza on the Portuguese throne.

Before becoming king, he was John II, the 8th Duke of Braganza. He was the grandson of Catherine, Duchess of Braganza, a claimant to the crown during the Portuguese succession crisis of 1580. On the eve of his death in 1656, the Portuguese Empire was at its territorial zenith, spanning the globe.

D. Sebastião José de Carvalho e Melo, 1st Marquis of Pombal and 1st Count of Oeiras (13 May 1699 – 8 May 1782), known as the Marquis of Pombal (Portuguese: Marquês de Pombal [mɐɾˈkeʒ ðɨ põˈbal]), was a Portuguese statesman and diplomat who despotically ruled the Portuguese Empire from 1750 to 1777 as chief minister to King Joseph I. A strong advocate for absolutism, and influenced by some of the ideals of the Age of Enlightenment, Pombal led Portugal's recovery from the 1755 Lisbon earthquake and reformed the kingdom's administrative, economic, and ecclesiastical institutions. During his lengthy ministerial career, Pombal accumulated and exercised autocratic power, curtailing individual liberties, suppressing political opposition, and fostering the Atlantic slave trade to Brazil. His cruel persecution of the Jesuits and Portuguese lower classes led him to be known as Nero of Trafaria, after a village he ordered to be burned with all its inhabitants inside, for refusing to follow his orders.

The son of a country squire and nephew of a prominent cleric, Pombal studied at the University of Coimbra before enlisting in the Portuguese Army, where he reached the rank of corporal. Pombal subsequently returned to academic life in Lisbon, but retired to his family's estates in 1733 after eloping with a nobleman's niece. In 1738, with his uncle's assistance, he secured an appointment as King John V's ambassador to Great Britain. In 1745, he was named ambassador to Austria and served until 1749. When Joseph I acceded to the throne in 1750, Pombal was appointed as Secretary of State for Foreign Affairs.

Dom João Manuel, Hereditary Prince of Portugal (Portuguese pronunciation: [ʒuˈɐ̃w mɐnuˈɛl]) (3 June 1537 – 2 January 1554) was a Portuguese infante (prince), the eighth child of King John III of Portugal by his wife Catherine of Austria, daughter of Philip I of Castile and Joanna of Castile. As the heir to the throne he was styled Prince of Portugal.

Dom Francisco de Almeida (Portuguese pronunciation: [fɾɐ̃ˈsiʃku ðɨ alˈmɐjðɐ]; c. 1450 – 1 March 1510), was a Portuguese nobleman, soldier and explorer. He distinguished himself as a counsellor to King John II of Portugal and later in the wars against the Moors and in the conquest of Granada in 1492. In 1505 he was appointed as the first governor and viceroy of the Portuguese State of India (Estado da Índia). Almeida is credited with establishing Portuguese hegemony in the Indian Ocean with his victory at the naval Battle of Diu in 1509. Before Almeida returned to Portugal he lost his life in a conflict with indigenous people at the Cape of Good Hope in 1510. His only son Lourenço de Almeida had previously been killed in the Battle of Chaul.

Dom Afonso VI (Portuguese pronunciation: [ɐˈfõsu]; 21 August 1643 – 12 September 1683), known as "the Victorious" (o Vitorioso), was the second king of Portugal of the House of Braganza from 1656 until his death. He was initially under the regency of his mother, Luisa de Guzmán, until 1662, when he removed her to a convent and took power with the help of his favourite, D. Luís de Vasconcelos e Sousa, 3rd Count of Castelo Melhor.

Afonso's reign saw the end of the Restoration War (1640–68) and Spain's recognition of Portugal's independence. He also negotiated a French alliance through his marriage. In 1668, his brother Pedro II conspired to have him declared incapable of ruling, and took supreme de facto power as regent, although nominally Afonso was still sovereign. Queen Maria Francisca, Afonso's wife, received an annulment and subsequently married Pedro. Afonso spent the rest of his life and reign practically a prisoner.