The region of England governed under Viking law after the 9th-century invasions was called the Danelaw.
The name refers both to a geographical area and to the legal customs associated with Danish rule. Viking armies conquered or controlled much of northern and eastern England, while Anglo-Saxon kings retained Wessex and other territories farther west and south. The boundary changed over time as rulers fought, negotiated, and reconquered land.
The Danelaw was not an independent Viking kingdom with one permanent capital. It contained important towns such as York, which Vikings called Jórvík, as well as settlements in East Anglia, the Five Boroughs, and Northumbria. Its Scandinavian influence remained visible in place-names, personal names, and vocabulary.
A common mix-up is treating the Danelaw as all Viking-controlled England. It was specifically the area where Danish law and customs had particular authority, rather than a simple name for every Viking settlement.