PORTO (OPORTO), DIOCESE of. — The diocese of P. or O. is situated in northwestern Portugal, between the dioceses of Braga, Vila Real, Lamego, Viseu, and Aveiro. Its episcopal see is located in the city of the same name, the second in Portugal after Lisbon. It has an area of 2,130 sq. km., with a population of 1,194,000, of whom 1,120,000 are Catholics, distributed among 457 parishes, with 623 diocesan priests and 150 religious priests; it has 19 male and 35 female religious communities (Ann. Pont., 1952, p. 324).
Perhaps the origins of the diocese of O. should be sought in the sixth century, immediately after the conversion of the Suebi. The oldest bishop of whom there is record is Viator, who signed the acts of the Second Council of Braga (572) with the title of bishop of Magneto (Meinedo), one of the churches of the diocese where the Cathedral was probably located at the beginning. The names of various bishops from the time of the Visigoths are also recorded. It seems that after the Arab invasion the bishops were merely titular, perhaps with the exception of Gomado, elected when Alfonso III took the city in 872.
The diocese was created by Pope Paschal II as a suffragan of Braga in 1114, the year in which Bishop Hugo was installed. Once he found himself at the head of the diocese, he sought to enlarge it through frequent disputes over boundaries with the archbishop of Braga and the bishop of Coimbra. He also obtained exemption from metropolitan jurisdiction from Paschal II by the rescript of 15 Aug. 1115, from then on having to submit directly to the Pope or to his legatus a latere.
During Hugo’s government the bishopric was also enriched by various donations, among them the celebrated one made by Queen Teresa of the burgo of P., with all its jurisdictions, revenues, and rights. The same Queen also donated the monasteries of Bouças and S. Marinha of Crestuma and the church of Regua. Unfortunately, these donations gave rise to no small number of conflicts between the bishop and Chapter on the one hand and the King and Municipality on the other. John I, king of Portugal, in agreement with Bishop Gil Alma, took the first steps toward resolving all the questions that had remained pending. In February 1405 they signed an agreement according to which the king, in exchange for dominion over the «burgo», would pay three thousand pounds annually. Innocent VII, by the bull Solet pia Mater (1 Oct. 1405), instructed the archbishop of Lisbon to suspend all excommunications should the agreement prove beneficial to the Church. The definitive agreement was signed one year later by the King, the Queen, and the heir Duarte on behalf of the civil authority, and by the bishop, the dean, and the Chapter on behalf of the ecclesiastical authority, with the clause concerning the three thousand pounds annually owed by the King remaining in force. In the time of Don Manuel the sum was reduced to 120 silver marks. From 1639 until 1671 the diocese remained vacant because the Holy See could not recognize the bishops presented by John IV. Finally, the dispute was settled after peace with Spain through the presentation and confirmation of Don Nicola Monteiro (1671–72). Joseph I, king of Portugal, obtained from Clement XIV (10 July 1770) the division of the diocese and the creation of the new diocese of Penafiel, which was suppressed by Pius VI in 1778.
The diocese is also one of the most celebrated in Portugal for its religious monuments, including the Cathedral, in the beautiful Romanesque style of the twelfth century; the church of S. Francesco, Gothic in style and dating from the fourteenth century; and the church of the Clerics, Baroque in style and dating from the eighteenth century.