William Embre Gaines (August 30, 1844 – May 4, 1912) was a U.S. Representative from Virginia.
Born near Charlotte Court House, Virginia, Gaines attended the common schools. During the Civil War enlisted as a private in Company K, Eighteenth Virginia Regiment (Pickett’, ands division). Reenlisted in the Army of the Cape Fear, and surrendered with Johnston, near Greensboro, North Carolina, in April 1865, having attained the rank of adjutant of Manly's artillery battalion. He studied law. He was admitted to the bar and practiced. He engaged in the tobacco business and banking at Burkeville, Virginia. He served as member of the Senate of Virginia from 1883 to 1887, when he resigned. He served as delegate to the Republican National Convention in 1884. He served as mayor of Burkeville. He served as delegate to several State conventions.
Gaines was elected as a Republican to the Fiftieth Congress (March 4, 1887-March 3, 1889). He was not a candidate for renomination in 1888. He died in Washington, D.C., May 4, 1912. He was interred in Glenwood Cemetery.