In 716 the Arabs began their invasion and conquest of Portugal, including Lisbon, Porto, Braga, Tuy, Lugo, and Orense.
On the recovery of Porto for Christianity, which was being promoted by the Burgundian Count Henry, son-in-law of King Alfonso VI of Castile and governor of the lands from the Minho River to the banks of the Tagus, priests and prelates were being imported, especially those with connections to Cluny in Burgundy.
He had been a Canon of the Cathedral of Compostella, and under the patronage of Bishop Diego Gelmirez, a Cluniac, he was said to have been a co-author of the Historia Compostellana.
He was ordained a priest on the day before Passion Sunday, and was consecrated a bishop on 23 March 1113 by Archbishop Mauricio Burdino of Braga, another Cluniac.
[22] As Bishop of Porto he secured from Pope Paschal II, by a bull granted on 15 August 1115, exemption of his diocese from the supervisory control of the Archbishop of Braga.
[23] He greatly enlarged his diocese and the cathedral patrimony increased by the donations he secured; thus, in 1120, he received from D. Theresa jurisdiction over the City of Porto with all the rents and dues thereof.
His successor, Pedro Salvadores, figured prominently in the questions between the clergy and King Sancho II, who refused to ecclesiastics the right of purchasing or inheriting land.
Finally, Pope Innocent IV committed the reform of abuses to Afonso III, brother of Sancho II who lost his crown.
Geraldo Domingues resigned in 1308 to act as counsellor of the King's daughter Constança, future Queen of Castile.
Other bishops were: John de Zambuja, or Estêvão; and Gil, who in 1406 sold the episcopal rights over Oporto to the Crown for an annual money payment, reduced in the reign of D. Manuel to 120 silver marks; Fernando Guerra, who in 1425 was created Archbishop of Braga; and Vasco.
Antão Martins de Chaves, who succeeded Vasco in 1430, was sent by the pope to Constantinople to induce the Greek emperor to attend the Council of Basle.
The see was then held by two brothers in succession, Diogo da Costa (1505-7) and D. Pedro da Costa (1511–39), who restored the bishop's palace and enriched the capitular revenues from his own purse; Belchior Beliago; and the Carmelite Frei Baltazar Limpo (1538–52), the fiftieth bishop.
In the time of Rodrigo Pinheiro, a learned humanist, Porto was visited by St. Francis Borgia and the Jesuits established themselves in the city.
Aires da Silva, ex-rector of Coimbra University, after ruling four years, fell in the battle of Alcácer Quibir in 1578 with King Sebastião.
Frei José Saldanha (1697–1708), famed for his austerity, never relinquished his Franciscan habit, a contrast to his successor Tomás de Almeida, who in 1716 became the first Patriarch of Lisbon.
Frei Manuel de Santa Inês, though elected, never obtained confirmation, but some years after his death, relations between Portugal and the Holy See were re-established by a concordat and Jerónimo da Costa Rebelo became bishop in 1843.
From 1854 to 1859 the see was held by António da Fonseca Moniz; on his death it remained vacant until 1862, when João de Castro e Moura, who had been a missionary in China, was appointed (d.1868).
A popular lawyer named Mesquita started a campaign against him, because the bishop refused to dismiss some priests; a reputed reactionary, who served the Aguardente Chapel, got himself elected judge of the Brotherhood of the Temple and provoked a great platform agitation with the result that the chapel was secularized and became a school under the patronage of the Marquis of Pombal Association.
In 1879 Américo was created cardinal and on his death (1911) Bishop António Barroso, an ex-missionary, was transferred from the see of Mylapore to that of Porto.