South Mimms is a village and former civil parish, now in the parish of South Mimms and Ridge, in the borough of Hertsmere in Hertfordshire in the East of England. It is a small settlement located near to the junction of the M25 motorway with the A1(M) motorway. In 2011 the parish had a population of 855.

Hertsmere is a local government district with borough status in Hertfordshire, England. Its council is based in Borehamwood. Other settlements in the borough include Bushey, Elstree, Radlett and Potters Bar. The borough contains several film studios, including Elstree Studios and the BBC Elstree Centre at Borehamwood. The borough borders Three Rivers, Watford, St Albans, and Welwyn Hatfield in Hertfordshire and the three north London boroughs of Harrow, Barnet and Enfield. Hertsmere is located mainly within the M25 Motorway.