Asa Harmon McCoy (1828-7 January 1865) was a Union Army soldier who served in the 45th Kentucky Mounted Infantry Regiment during the American Civil War. The brother of Randolph McCoy, he joined the Unionist Pike County Home Guards during the early months of the war, during which he sustained a gunshot wound to the cest. He later joined the 45th Kentucky on 20 October 1863, and he was captured by Confederates on 5 December 1863 before being released four months later. In December 1864, he was mustered out of the service, but, on his return to his Pike County home, he was murdered by Jim Vance and a group of Confederate guerrillas after Vance confronted McCoy about wearing his Union uniform into his saloon. His murder by Vance, Devil Anse Hatfield's uncle, sparked the Hatfield-McCoy feud. His daughter Nancy McCoy later married Devil Anse's son Johnse McCoy in 1887; his son Jefferson McCoy was later murdered by Cap Hatfield and Tom Wallace.