William Frederick Kopp (June 20, 1869 – August 24, 1938) was a six-term Republican U.S. Representative from Iowa's 1st congressional district. Born near Dodgeville, Iowa, Kopp attended the common schools. He was graduated from Iowa Wesleyan College at Mount Pleasant in 1892 and from the University of Iowa College of Law at Iowa City in 1894. He was admitted to the bar in 1894 and commenced practice in Mount Pleasant. He served as prosecuting attorney of Henry County, Iowa, from 1895 to 1899. He later served as Postmaster of Mount Pleasant from 1906 to 1914, and as a member of the board of trustees of Iowa Wesleyan College from 1908 to 1938.