Daniel A. Greenberg (28 September 1934 – 2 December 2021), was one of the founders of the Sudbury Valley School, has published several books on the Sudbury model of school organization, and was described by Sudbury Valley School trustee Peter Gray as the “principal philosopher” among its founders. He was a physics professor at Columbia University, and was described by Lois Holzman as the school’s “chief ‘philosophical writer’”.