Osraige, also known as Osraighe or Ossory (modern Irish: Osraí), is a medieval Irish kingdom comprising most of present-day County Kilkenny and western County Laois.
The home of the Osraige people, it exists from around the first century until the Norman invasion of Ireland in the twelfth century.
It is ruled by the Dál Birn dynasts, whose medieval descendants assume the surname Mac Giolla Phádraig.
The name survives in the Catholic Diocese of Ossory, established in the fifth century, which continues to use roughly the same borders.
According to tradition, Osraige was founded by Óengus Osrithe in the first century and was originally within Leinster's polity.
In the fifth century, the Corcu Loígde of Munster displace the Dál Birn and bring Osraige under Munster's direct control.
The Dál Birn return to power in the seventh century, though Osraige remains nominally part of Munster until 859, when it achieves formal independence under the powerful king Cerball mac Dúnlainge.
Osraige's rulers remain major players in Irish politics for the next three centuries, though they never vie for the High Kingship.
In the early twelfth century, dynastic infighting fragment the kingdom, and it is re-adjoined to Leinster.
The Normans under Strongbow invade Ireland beginning in 1169, and most of Osraige collapses under pressure from Norman leader William Marshal.
The northern part of the kingdom, eventually known as Upper Ossory, survives intact under the hereditary lordship until the reign of King Henry VIII of England, when it is formally incorporated as a barony of the same name.
