William Thetford (April 25, 1923 – July 4, 1988) was an American psychologist, medical psychologist and professor. He is best known for his collaboration with Helen Schucman in typing the original manuscript and being on the editing team for A Course in Miracles (ACIM), a self-study curriculum in spiritual psychology. He died in 1988, aged 65, in Tiburon, California, after having made his involvement with the ACIM material and its study the most central focus of his life.