William Willis Garth (October 28, 1828 – February 25, 1912) was an American politician. He served as a representative of the Alabama's 8th Congressional District in the U.S. House of Representatives between March 4, 1877, and March 3, 1879. Garth was elected in 1876 as a Democratic representative to the 45th Congress, but was defeated for reelection in 1878. He resumed the practice of law, and died in Huntsville, Alabama on February 25, 1912. He was buried in Maple Hill Cemetery in Huntsville.