From 1967, the diocese has had both a titular Cardinal bishop, and a resident bishop, who handles the diocesan business. The resident bishops have been:
Porto was in ancient times Portus, the chief harbour of Rome. It owes its origin to the port built by Claudius on the right of the Tiber, opposite Ostia; Trajan enlarged the basin, and in a short time there grew around it a city which soon became independent of Ostia.
It was near Porto that Julius Nepos compelled Emperor Glycerius to abdicate (474). During the Gothic War the town served the Goths (537 and 549) and the Byzantines (546-52) as a base of operations against Rome. In the ninth and tenth centuries it was sacked on several occasions by the Saracens. In 849 Pope Leo IV fortified it and established there a colony of Corsicans for the defence of the coast and the neighbouring territory; but the city continued to decay.
Christianity was early established there. Several martyrs of Porto are known, including Herculanus, Hyacinthus, Martialis, Saturninus Epictetus, Maprilis and Felix. The place was also famous as the probable see of St. Hippolytus.
In 314 Gregorius was bishop. The great xenodochium, or hospice, of Pammachius was built about 370. Among the other bishops should be mentioned
Santa Rufina grew up around the basilica of the Holy Martyrs Sts. Rufina and Secunda on the Via Aurelia, fourteen miles (21 km) from Rome; the basilica is said to have been begun by Pope Julius I, and was finished by Saint Damasus. In the ninth century this town was destroyed by the Saracens, and the efforts of Pope Leo IV and Pope Sergius III were unable to save it from total ruin: all that remains are the remnants of the ancient basilica and a chapel.
The first notice of it as an episcopal see dates from the fifth century, when its bishop Adeodatus was present at the councils held by Pope Symmachus; its bishop St. Valentinus, Vicar of Rome during the absence of Pope Vigilius, had his hands cut off by Totila. Among its other bishops mention should be made of
The residence of the bishops of Silva Candida was on the Insula Tiberina beside the church of Sts. Adalbert and Paulinus, while that of the bishops of Porto was on the same island near the church of San Giovanni. The bishops of Silva Candida, moreover, enjoyed great prerogatives in relation with the ceremonies of the basilica of St. Peter.
The most famous of these prelates was Cardinal Humbertus, who accompanied Leo IX from Burgundy to Rome; he was appointed Bishop of Sicily by that pope, but, having been prevented by the Normans from landing on the island, he received the See of Silva Candida, and later was sent to Constantinople to settle the controversies aroused by Michael Cærularius. He wrote against the errors of the Greeks and against Berengarius (1051-63).
The last Bishop was Mainardus.
Historically, the Bishop of Porto became the second cardinal, the Bishop of Ostia being the first, and officiated on Mondays in the Lateran Basilica; he obtained, moreover, the other rights of the Bishop of Santa Rufina, but lost jurisdiction over the Leonine City and its environs, when they were united to the city of Rome.
In 1826, Civitavecchia was separated from the Diocese of Viterbo and Toscanella and united with that of Porto, but in 1854, with Corneto, it was made an independent see. Mention should be made of the Cardinal Bishop of Porto Luigi, Lambruschini (1847), who restored the cathedral and the episcopal palace.
From the sixteenth century, the incumbency of prelates of this see was, as a rule, of short duration, because most of the cardinal-bishops preferred the See of Ostia and Velletri, which they exchanged for their own as soon as possible.
The Diocese of Cære, now Cerveteri, has been united with that of Porto since the twelfth century. Cære was an ancient city, called at first Agylla, where the sanctuaries of Rome and the Vestals were hidden during the invasion of the Gauls; the Etruscan tombs scattered about its territory are important archleologically. Cervetri had bishops of its own until the eleventh century; the first was Adeodatus (499), assuming that he was not the Adeodatus who signed himself Bishop of Silva-Candida in the third synod of Pope Symmachus (501). The last known was Benedictus, referred to in 1015 and 1029. The Diocese of Porto and Santa Rufina has 18 parishes, with 4600 inhabitants.
Salvador Miranda: List of cardinal-bishops of Porto e S. Rufina
Pius Bonifacius Gams, Series episcoporum Ecclesiae catholicae, Leipzig 1931, pp. VIII-XI