| William Willis Garth | |
| State: | Alabama |
| Term Start: | March 4, 1877 |
| Term End: | March 3, 1879 |
| Predecessor: | Constituency established |
| Successor: | William M. Lowe |
| Birth Date: | 28 October 1828 |
| Birth Place: | Morgan County, Alabama, U.S. |
| Death Place: | Huntsville, Alabama, U.S. |
| Resting Place: | Maple Hill Cemetery |
| Party: | Democratic |
| Education: | University of Virginia |
| Allegiance: | Confederate States |
| Branch: | Confederate States Army |
| Serviceyears: | 1861–1865 |
| Rank: | Lieutenant colonel |
| Battles: | American Civil War |
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 born on October 28, 1828, in Morgan County, Alabama. He pursued classical studies at Lagrange, Virginia and at Emory and Henry College, Emory, Virginia, and studied law at the University of Virginia. He was admitted to the Alabama bar and practiced law at Huntsville, Alabama. During the Civil War, he served as a lieutenant colonel on the staff of General James Longstreet in the Confederate Army.
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.