William Frederick Kopp (June 20, 1869 – August 24, 1938) was a six-term Republican U.S. Representative from Iowa's 1st congressional district.

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.

Kopp was elected to the Iowa House of Representatives in 1914, and served a single two-year term that ended in early 1917.

In 1920, Kopp was elected as a Republican to the first of six consecutive terms in the U.S. House, representing Iowa's 1st congressional district in the Sixty-seventh and to the five succeeding Congresses.

This article incorporates public domain material from the Biographical Directory of the United States Congress