Clayton Byron Simmons (October 11, 1876 – July 24, 1922) was an American osteopath and college football and college basketball coach. He served as the head football coach Iowa State Normal School—renamed Iowa State Teachers College in 1909 and now known a s University of Northern Iowa—in Cedar Falls, Iowa from 1908 to 1909 and at the First District Normal School—commonly known then as Kirksville Normal now known as Truman State University—in Kirksville, Missouri from 1910 to 1911, compiling a career college football coaching record of 14–9. Simmons was also the head basketball coach at Iowa State Teachers for one season, in 1909–10, tallying a mark of 4–3.