Coordinates: 51°16′25″N 0°46′00″W / 51.27361°N 0.7666667°W / 51.27361; -0.7666667

BAE Systems plc (LSE: BA.) is a British multinational defence, security and aerospace company headquartered in London, United Kingdom, that has global interests, particularly in North America through its subsidiary BAE Systems Inc. BAE is among the world's largest military contractors; in 2009 it was the second-largest based on revenues. It was formed on 30 November 1999 by the £7.7 billion merger of two British companies, Marconi Electronic Systems (MES), the defence electronics and naval shipbuilding subsidiary of the General Electric Company plc (GEC), and aircraft, munitions and naval systems manufacturer British Aerospace (BAe).

BAE Systems is the successor to various aircraft and defence electronics companies, including The Marconi Company, the first commercial company devoted to the development and use of radio; A.V. Roe and Company, one of the world's first aircraft companies; de Havilland, manufacturer of the world's first commercial jet airliner; British Aircraft Corporation, co-manufacturer of the Concorde supersonic transport; and Supermarine, manufacturer of the Spitfire. Since its formation it has sold its shares in Airbus, Astrium, AMS and Atlas Elektronik, and made a number of acquisitions, most notably United Defense and Armor Holdings of the United States.