Portchester is a village in the borough of Fareham in Hampshire, England. It is 4 miles (6.4 km) northwest of Portsmouth and around 18 miles east of Southampton on the A27 road. Its population according to the 2011 United Kingdom census was 17,789.

The Borough of Fareham is a local government district with borough status in Hampshire, England. Its council is based in Fareham. Other places within the borough include Portchester, Hill Head, Sarisbury, Stubbington, Titchfield and Warsash. The borough covers much of the semi-urban area between the cities of Southampton and Portsmouth, and is part of the South Hampshire conurbation. The neighbouring districts are Eastleigh, Winchester, Portsmouth and Gosport. The district's southern boundary is the coast of the Solent.