Southwick House

Southwick House is a manor house of the Southwick Estate located just to the north of Portsmouth in Hampshire, England. The house was built in 1800 in the late Georgian style, to replace Southwick Park house. The house is distinct for its two-story foyer lit from a cupola, and a series of elliptical rooms. A hemi-circular portico is centered on the house's colonnade of paired Ionic columns.

The house became important during World War II. In 1940 the estate owners allowed the Royal Navy to use the house to accommodate overnight pupils of the Royal Navy School of Navigation, HMS Dryad in Portsmouth Naval Dockyard. In 1941, after heavy bombing of the dockyard, the house was requisitioned and became the new home of HMS Dryad. In 1943, with the planning for D-Day already underway, the house was chosen to be the location of the advance command post of the Supreme Headquarters Allied Expeditionary Force. Because of this, HMS Dryad was moved out of the house onto further land requisitioned from the estate. In 1944, in the months leading up to D-Day, the house became the headquarters of the main allied commanders, including Naval Commander-in-Chief Admiral Ramsay, Allied Supreme Commander General Eisenhower and Army Commander-in-Chief General Montgomery.

After the war HMS Dryad remained on site, with the house becoming the wardroom. In 2004 the functions of HMS Dryad were transferred to HMS Collingwood in Fareham and the site reverted to its original name of Southwick Park. Since then it has been home to the tri-Service Defence College of Policing and Guarding.

The large wall maps that were used in planning D-Day are still in place in the house, with the various markers showing the positions of the involved forces at the moment the first landing commenced.

In November 2016 the Ministry of Defence announced that the site would close in 2025.