The Horsham Constituency is home to an electorate of 86,730 voters (December 2019). The constituency lies wholly within West Sussex and, at a local-government level, is the responsibility of West Sussex County Council at County level. In terms of District Councils, the constituency is mostly administered by Horsham District Council; however, the part of the constituency that is to the east of the A23 falls under the responsibility of Mid Sussex District Council.
Under the structure of West Sussex County Council, the constituency takes in the following nine Divisions wholly within its boundaries;
- Horsham East
- Horsham Hurst
- Horsham Riverside
- Southwater and Nuthurst
- St Leonards Forest
- Worth Forest
In addition the Division of Imberdown falls partly into the parliamentary constituency of Mid Sussex.
Under the structure of Horsham District Council, the constituency takes in the following 15 Wards wholly within its boundaries;
- Broadbridge Heath
- Colgate and Rusper
- Holbrook East
- Holbrook West
- Itchingfield, Slinfold and Warnham
- Roffey North
- Roffey South
- Southwater North
- Southwater South and Shipley
Under the structure of Mid Sussex District Council, the constituency takes in the following three Wards wholly within its boundaries;
- Ardingly and Balcombe
- Copthorne and Worth
- Crawley Down and Turners Hill
The constituency is located in a northern part of West Sussex, bordering the two constituencies of Arundel and South Downs and Chichester to the south and west, Mid Sussex to the south and east, Crawley and Mole Valley to the north and also sections of Guildford, Chichester and East Surrey. It is centred slightly east of the town of Horsham and is rectangular with the exception of a noticeable gap formed by the geographically smaller constituency of Crawley.
The parliamentary constituency of Horsham has returned a Conservative Member of Parliament ever since 1880. Horsham District Council and Mid Sussex District Council are both Conservative-controlled as is West Sussex County Council.