Muscoe Russell Hunter Garnett (July 25, 1821 – February 14, 1864), was a nineteenth century politician and lawyer from Virginia.
Garnett was the son of James Mercer Garnett and Maria (Hunter) Garnett. He was the grandson of James M. Garnett and nephew of Robert Mercer Taliaferro Hunter. He was born on his family’s "Elmwood" estate (located near Loretto, Virginia). He attended the University of Virginia, where he received his law degree in 1842. Garnett was admitted to the Virginia bar in 1842, and set up practice, as his father had done, in Loretto. 
He was a delegate to the Virginia Constitutional Convention in 1850 and 1851. During that time (in 1850), he wrote a pamphlet The Union, Past and Future; how it works and how to save it. By a Citizen of Virginia, which discussed the relationship of slavery to the national government.
Prior to his election to Congress, he was a Virginia delegate to both the 1852 and 1856 Democratic National Conventions, a member of the Virginia House of Delegates (from 1853–1856), and a member of the Board of Visitors of the University of Virginia (from 1855–1859).
He was married in July 26, 1860, to Mary Picton, daughter of Edwin Stevens. They had two children before his early death: James Mercer Garnett, born July 7, 1861, and Mary Barton Picton Garnett, born May 28, 1863.
In 1856, Garnett was elected as a Democrat from Virginia's 1st Congressional District to the 34th Congress to fill the vacancy caused by the death of Thomas H. Bayly. He was subsequently reelected to both the 35th and 36th Congresses, serving from December 1, 1856, to March 3, 1861, only leaving at the outbreak of the Civil War.
With his sympathies lying with the South, he became a delegate to first the Virginia secession convention and then to the State constitutional convention in 1861. From 1862–1864, he was as a Virginian member of the First Confederate Congress. During that same time, his uncle Robert Hunter was the CSA Secretary of State and then a CSA Senator. While attending the Confederate Congress in early 1864, Muscoe caught typhoid fever, and subsequently died at his family's "Elmwood" estate on February 14, 1864, where he was buried in the family cemetery.