Northumberland () is a ceremonial county and historic county in North East England. It is bordered by Cumbria to the west, County Durham and Tyne and Wear to the south and the Scottish Borders to the north. To the east is the North Sea coastline with a path 103 kilometres (64 mi) long. The county town is Alnwick. The county is administered as a unitary authority by Northumberland County Council, headquartered in Morpeth.
The county of Northumberland included Newcastle upon Tyne until 1400, when the city became a county of itself. Northumberland expanded greatly in the Tudor period, annexing Berwick-upon-Tweed in 1482, Tynedale in 1495, Tynemouth in 1536, Redesdale around 1542 and Hexhamshire in 1572.Islandshire, Bedlingtonshire and Norhamshire were incorporated into Northumberland in 1844.Tynemouth and other settlements in North Tyneside were transferred to Tyne and Wear in 1974 under the Local Government Act 1972.
Lying on the Anglo-Scottish border, Northumberland has been the site of a number of historic battles. The county is noted for its undeveloped landscape of high moorland, now largely protected as the Northumberland National Park. Northumberland is the least densely populated county in England, with only 62 people per square kilometre.