The Philip A. Hart Senate Office Building is the third U.S. Senate office building, and is located on 2nd Street NE between Constitution Avenue NE and C Street NE in Washington, D.C., in the United States. Construction began in January 1975, and it was first occupied in November 1982. Rapidly rising construction costs plagued the building, creating several scandals. The structure is named for Philip Hart, who served 18 years as a senator from Michigan. Accessed via a spur of the United States Capitol Subway System, the building features a nine-story atrium dominated by massive artwork, and a large Central Hearing Facility which provides television facilities as well as extensive seating.

The United States Senate is the upper chamber of the United States Congress. The United States Senate and the lower chamber of Congress, the United States House of Representatives, comprise the federal bicameral legislature of the United States. Together, the Senate and the House maintain authority under Article One of the U.S. Constitution to pass or defeat federal legislation. The Senate has exclusive power to confirm U.S. presidential appointments, approve or reject treaties, and try cases of impeachment brought by the House. The Senate and the House provide a check and balance on the powers of the executive and judicial branches of government.