William Emerson Brock (March 14, 1872–August 5, 1950) was a Democratic United States Senator from Tennessee from 1929 to 1931. (Later his grandson, William Emerson Brock III, popularly known was Bill Brock, was a Republican Congressman and Senator from Tennessee.)

Brock was born in Davie County, North Carolina, where he attended public school and engaged in agricultural pursuits until 1894. In that year, he moved to Winston-Salem, North Carolina and became a clerk in a general store. From 1896 until 1901 he worked as a tobacco salesman. In 1909 he moved to Chattanooga, Tennessee. In Chattanooga, Brock became involved in candy manufacturing, and also had involvments in insurance and banking interests. He became a trustee of the former University of Chattanooga, now the University of Tennessee at Chattanooga, Emory and Henry College, and also Martha Washington College . On September 2, 1929 Brock was appointed to the vacancy in the Senate caused by the death of Senator Lawrence D. Tyson by governor of Tennessee Henry Hollis Horton. On November 4, 1930, Brock was elected to the balance of this term. He did not run for the new term, and his service as Senator ended on March 3, 1931. He was succeeded by Cordell Hull. He returned to his Chattanooga candy manufacturing business and remained involved in its operation until his death in 1950.