The former Irish Catholic diocese of Ross was in south-west Ireland. It existed until 1958, when it was merged into the diocese of Cork and Ross.
This see was founded by St. Fachtna, and the place-name was variously known as Roscairbre and Rosailithir (Ross of the pilgrims). St. Fachtna founded the School of Ross as well as the see; and his death occurred about 590, on 14 August, on which day his feast is celebrated.
The succession of bishops was uninterrupted till after the Reformation period. John of England in 1207 granted the cantred of Rosailithir to David Roche, regardless of the claims of the native chief, the O'Driscoll, but the episcopal manors were left undisturbed. In 1306, the value of the bishop's mensa was 26 marks, while the cathedral was valued at 3 marks; and the tribal revenue of the see was but 45 pounds sterling. The number of parishes was 29, divided into 3 divisions; and there was a Cistercian abbey, Carrigilihy (de fonte vivo); also a Benedictine Priory at St. Mary's, Ross. The Franciscans acquired a foundation at Sherkin Island from the O'Driscolls in 1460.
Blessed Thady MacCarthy was appointed Bishop in 1482, but was forcibly deprived of his see in 1488. However he was translated to the united diocese of Cork and Cloyne in 1490; was again a victim of political intrigues, and died a confessor at Ivrea in 1492, being beatified in 1895. In 1517 the revenue of the diocese was but 60 marks. At that date the chapter was complete with 12 canons and 4 vicars, and there were 27 parishes, including three around Berehaven.
Thomas O'Herlihy assisted at the Council of Trent, and ruled from 1562 till his death on 11 March, 1580. It was not until 1581 that Elizabeth I of England appointed a Protestant prelate under whom, in 1584, the Sees of Cork and Cloyne were annexed to Ross. However, in the Catholic arrangement Ross continued independent, and Owen MacEgan died a confessor in January, 1602-3. In 1625 the bishop (de Torres) was a Spaniard, who ruled his diocese through a vicar-general.
In 1647 the nave and tower of the cathedral were levelled by the Puritans; and Bishop MacEgan was hanged by Lord Broghill, on 10 April, 1650. At length, in 1693, Bishop Sleyne of Cork was given Ross in commendam, and the see continued under his successors till 1748, when it was united to Cloyne under Bishop O'Brien. From 1748 Ross was administered by the Bishop of Cloyne, but it regained its autonomy under Bishop Crotty, and in 1857 Bishop O'Hea was consecrated to Ross. During the episcopate of Dr. O'Hea the episcopal see was transferred to Skibbereen. He was followed by William Fitzgerald (1877-97) and Denis Kelly.