It was formed early in the twelfth century out of the southern portion of the Diocese of Bergen, which had included until then the whole of Western Norway (Gulathingslagen). Reginald, an Englishman and most probably a Benedictine monk from Winchester Cathedral, was the first Bishop of Stavanger. With the money given him in 1128 by King Sigurd Jorsalefarer, for allowing that monarch to marry one Cecilia during the lifetime of his consort Queen Malmfrid, Reginald began the cathedral and founded the chapter. He was hanged at Bergen in 1135 by King Harald Gille upon his refusing to pay fifteen marks of gold to that monarch, who suspected him of concealing the treasures belonging to King Magnus IV of Norway.
Reginald's successor, John Birgerssön, was translated to the archdiocese of Trondhjem in 1152, as was also Bishop Eric Ivarssön in 1188. The great quarrel lasting from 1294 to 1303, which Bishop Arne (1276-1303) had with his chapter, was terminated only by the intervention of King Haakon, who decided in favour of the chapter and decreed, among other things, that they should have a voice in all nominations to, and deprivations of, benefices in the diocese. Bishop Gutterm Paalssön (1343-50) died of the Black Death. His successor, Arne Aslakssön, also died suddenly at Avignon, where he had gone to seek a dispensation super defectu natalium.
Consequently Pope Clement VI appointed Sigfrid, a Swedish Dominican, Bishop of Stavanger by papal provision in 1351. Most of his successors were appointed in the same way after agreement with the king. In 1352 Sigfrid was transferred to Oslo, while Gyrd Aslessön, who had just been appointed to that bishopric, had to accept in 1354 the less lucrative See of Stavanger. He was soon succeeded by Botolph Asbjornssön (1355-81), who gave his library to the chapter and compiled a Domesday Book (Jordebog) for the diocese. It has since disappeared. Bishop Audum Eivindssön (1426-55) built many churches and gave the episcopal tithes of Valdres to the Brigittines of Munkalif Abbey near Bergen in 1441 in their hour of need. The last Catholic bishop was Hoskold Hoskoldssön (1513-37), who was taken prisoner by Thord Rod at Bergen and died there.
The only monastery of importance was the Augustinian Abbey of Utstein founded about 1280. The bishops of Stavanger had many disputes with the abbots of Utstein. In 1537 the abbey was handed over to Thrond Ivarssön, who had, however, to maintain the monks. Other monasteries are said to have existed in the Diocese of Stavanger, but little or nothing is known of them. There was a hospital dedicated to St. Peter at Stavanger itself.