Coordinates: 55°58′N 4°32′W / 55.96°N 4.53°W / 55.96; -4.53

Dunbartonshire (Siorrachd Dhùn Bhreatainn in Gaelic) or the County of Dumbarton is a lieutenancy area and registration county in the west central Lowlands of Scotland lying to the north of the River Clyde. Until 1975 it was a county used as a primary unit of local government with its county town and administrative centre at the town of Dumbarton. The area had been previously been part of the historic district of Lennox, which was a duchy in the Peerage of Scotland related to the Duke of Lennox.

In modern local government, the county is divided into two of the thirty-two council areas of Scotland, namely East Dunbartonshire, with its administrative headquarters at Kirkintilloch, and West Dunbartonshire, with its administrative centre at Dumbarton.

Dumbarton was the county town from which the name of Dunbartonshire derives. The name of the town comes from the Scottish Gaelic Dùn Breatainn meaning "fort of the Britons".

Historically, the spelling of the county town and the county were not standardised. By the 18th century the names "County of Dunbarton" and "County of Dumbarton" were used interchangeably. Different county bodies used the two spellings: the Dunbarton County Constabulary were formed in 1857 by the Commissioners of Supply for the County of Dunbarton. Dumbartonshire County Council, set up under the Local Government (Scotland) Act 1889 adopted the spelling "Dunbartonshire" by 1914, a fact recognised by the Local Government (Scotland) Act 1947.

West Dunbartonshire (Scots: Wast Dunbartonshire; Scottish Gaelic: Siorrachd Dhùn Bhreatainn an Iar, pronounced [ʃirˠəxk ɣumˈpɾʲɛʰt̪ɪɲ ə ɲiəɾ]) is one of the 32 local government council areas of Scotland. The council area borders onto the west of the City of Glasgow and contains many of Glasgow's commuter towns and villages as well as the city's suburbs. West Dunbartonshire also borders onto Argyll and Bute, Stirling, East Dunbartonshire and Renfrewshire.

The area was formed on 1 April 1996 from part of the former Strathclyde Region, namely the entire district of Clydebank and the Dumbarton district less the Helensburgh area. In the Local Government etc. (Scotland) Act 1994 that created the council area its name was Dumbarton and Clydebank. The council elected as a shadow authority in 1995 resolved to change the name of the area to West Dunbartonshire.

The area is essentially composed of three parts: the towns of Dumbarton and Clydebank and the Vale of Leven district.

West Dunbartonshire is administered from Dumbarton, although Clydebank is the largest town.