Scandinavian York (also referred to as Scandinavian Jórvík) is a term used by historians for the south of Northumbria during the period of the late 9th century and first half of the 10th century, when it was dominated by Norse warrior-kings; in particular, used to refer to the city controlled by these kings.
Norse monarchy controlled varying amounts of Northumbria from 875 to 954, however the area was invaded and conquered for short periods by England between 927 and 954 before eventually being annexed into England in 954. It was closely associated with the much longer-lived Kingdom of Dublin throughout this period.
York had been founded as the Roman legionary fortress of Eboracum and revived as the Anglo-Saxon trading port of Eoforwic. It was first captured in November 866 by Ivar the Boneless, leading a large army of Danish Vikings, called the "Great Heathen Army" by Anglo-Saxon chroniclers, which had landed in East Anglia and made their way north, aided by a supply of horses with which King Edmund of East Anglia bought them off and by civil in-fighting between royal candidates in the Anglian Kingdom of Northumbria between the leaders of its two sub-kingdoms; Bernicia and Deira. Declaring a truce, the rivals for the throne of Northumbria joined forces but failed to retake the city in March 867, and with their deaths Deira came under Danish control as the Kingdom of Northumbria and the Northumbrian royal court fled north to refuge in Bernicia.