George Brecht (August 27, 1926 – December 5, 2008), born George Ellis MacDiarmid, was an American conceptual artist and avant-garde composer, as well as a professional chemist who worked as a consultant for companies including Pfizer, Johnson & Johnson, and Mobil Oil. He was a key member of, and influence on, Fluxus, the international group of avant-garde artists centred on George Maciunas, having been involved with the group from the first performances in Wiesbaden 1962 until Maciunas' death in 1978.