Peter T. Demos (July 18, 1918 – September 18, 2012) was a professor in the Department of Physics and the Laboratory for Nuclear Science at MIT. A native of Peterborough, Ontario, Demos attended Peterborough Collegiate and Vocational School and Queen's University, and received a Ph.D. in Physics from MIT in 1951. He was a founder and former director of the Bates Linear Accelerator at MIT and served as advisor on nuclear science to John F. Kennedy.