Hertsmere is a local government district and borough in Hertfordshire, England. Its council is based in Borehamwood. Other towns in the borough include Bushey, Elstree, Radlett and Potters Bar.
The district was formed on 1 April 1974, under the Local Government Act 1972, by a merger of the former area of Bushey Urban District and Potters Bar Urban District with Elstree Rural District and part of Watford Rural District (the parish of Aldenham).
The name "Hertsmere" was invented for the new district by combining the common abbreviation of "Hertfordshire" ("Herts") with "mere", an archaic word for boundary. The name is doubly appropriate as the district straddles the historic county boundary between Middlesex and Hertfordshire and forms the administrative boundary between Hertfordshire and Greater London. The name is reflected in the council's coat of arms, which shows a hart upon the battlements of a boundary wall.
The district was awarded borough status by Royal Charter in 1977.
Hertsmere is a constituency identical with the area of the Hertsmere Borough of Hertfordshire in England represented since 2010 in the House of Commons of the UK Parliament by Oliver Dowden of the Conservative Party.
1983-1997: The Borough of Hertsmere, and the City of St Albans ward of London Colney.
1997-present: The Borough of Hertsmere.
Since 1997 the constituency is coterminous with the borough of Hertsmere, in southern Hertfordshire (before then it had also included one electoral ward from the City of St Albans district). Hertsmere consists of the major towns and villages of Bushey, Radlett, Potters Bar and Borehamwood, elevated settlements above the headwaters of the River Colne which forms much of the northern border. Bushey borders Watford and the London Borough of Harrow to the west and south west, while Potters Bar borders Barnet and Broxbourne on the east. Borehamwood is just south-east of the centre, the largest town in the constituency — in the north and centre is Radlett, separated by two large villages and farms from St Albans to the north.