Hertfordshire (/ˈhɑːrt.fərd.ʃɪər -.ʃər/ , HART-fərd-sheer -shər; often abbreviated Herts) is a ceremonial county in the East of England. It borders Bedfordshire to the north-west, Cambridgeshire to the north-east, Essex to the east, Greater London to the south and Buckinghamshire to the west. The largest settlement is Watford.
The county has an area of 634 square miles (1,640 km) and had an estimated population of 1,236,191 in 2024. Watford is located in the south-west, and the county's other settlements include Stevenage in the north, the city of St Albans in the centre, and Hemel Hempstead in the west. For local government purposes Hertfordshire is a non-metropolitan county with ten districts. Potters Bar in the south-east of the county was historically part of Middlesex.