Osraige (Old Irish) or Osraighe (Classical Irish), Osraí (Modern Irish), anglicized as Ossory, was a medieval Irish kingdom comprising what is now County Kilkenny and western County Laois, corresponding to the Diocese of Ossory. The home of the Osraige people, it existed from around the first century until the Norman invasion of Ireland in the 12th century. It was ruled by the Dál Birn dynasty, whose medieval descendants assumed the surname Mac Giolla Phádraig. According to tradition, Osraige was founded by Óengus Osrithe in the 1st century and was originally within the province of Leinster. In the 5th century, the Corcu Loígde of Munster displaced the Dál Birn and brought Osraige under Munster's direct control. The Dál Birn returned to power in the 7th century, though Osraige remained nominally part of Munster until 859, when it achieved formal independence under the powerful king Cerball mac Dúnlainge. Osraige's rulers remained major players in Irish politics for the next three centuries, though they never vied for the High Kingship. In the early 12th century, dynastic infighting fragmented the kingdom, and it was re-adjoined to Leinster. The Normans under Strongbow invaded Ireland beginning in 1169, and most of Osraige collapsed under pressure from Norman leader William Marshal. The northern part of the kingdom, eventually known as Upper Ossory, survived intact under the hereditary lordship until the reign of King Henry VIII of England, when it was formally incorporated as a barony of the same name. Geography The ancient Osraige inhabited the fertile land around the River Nore valley, occupying nearly all of what is modern County Kilkenny and the western half of neighbouring County Laois. To the west and south, Osraige was bounded by the River Suir and what is now Waterford Harbour; to the east, the watershed of the River Barrow marked the boundary with Leinster (including Gowran); to the north, it extended into and beyond the Slieve Bloom Mountains. These three principal rivers- the Nore, the Barrow, and the Suir, which unite just north of Waterford City, were collectively known as the "Three Sisters" (). Like many other Irish kingdoms, the tribal name of Osraighe also came to be applied to the territory they occupied; thus, wherever the Osraige dwelt became known as Osraige. The kingdom's most significant neighbours were the Loígis, Uí Ceinnselaig and Uí Bairrche of Leinster to the north and east and the Déisi, Eóganacht Chaisil and Éile