James Forrestal Energy Department Building

The James V. Forrestal Building is a low-rise Brutalist office building located in Washington, D.C., in the United States. Originally known as Federal Office Building 5, and nicknamed the Little Pentagon, the Forrestal Building was constructed between 1965 and 1969 to accommodate United States armed forces personnel. It is named after James Forrestal, the first United States Secretary of Defense. It became the headquarters of the United States Department of Energy after that agency's creation in 1977.

The 1,688,484-square-foot Forrestal Building is located at 1000 Independence Avenue SW. It consists of three structures: an East Building with eight floors above ground, the North Building with four floors above ground, and a West Building with two floors above ground. All three structures are connected by two floors of underground office space. In order to provide access to L'Enfant Plaza, the North Building is raised up on 35-foot-high pilotis.