Henry Gregor Felsen (1916 - 1977) was an American writer, particularly of children's books.
Felsen was born and attended school in Brooklyn, the son of Harry and Sabina Bedrick Felsen. He attended the University of Iowa for two years, where he met his first wife Penny, from whom he was later divorced. After struggling financially during the Depression, Felsen sold nine books and hundreds of stories in his first eighteen months of full-time freelance writing in the early 1940s. After war service with the Marine Corps, during which he edited the corps magazine Leatherneck and also wrote magazine articles while stationed in the Pacific, he returned to Iowa where he lived for most of the rest of his life. He taught part time at the Drake University (1964-1969), and in 1977 left Iowa to spend his remaining years travelling. His second wife Karen survived him, as did a son and daughter from his first marriage, and two step-children.
His best-selling book was Hot Rod, one of a series that also included Street Rod and Crash Club and sold about eight million copies in all. He wrote about 60 books, many of them moralistically exploring the evils of drugs, sexism and racism.
He is also credited with one screenplay, for the 1968 film Fever Heat which was based on his novel of the same name which had been published under the pen name of Angus Vicker.