Boyd County is a county located in the U.S. Commonwealth of Kentucky. As of the 2020 census, its population was 48,261. The county seat is Catlettsburg, and its largest city is Ashland. The county was formed in 1860. The county spans 160 square miles, and is found at the northeastern edge of the state, near the Ohio River and Big Sandy River and situated in mountainous Appalachia. Boyd County is in the Huntington-Ashland, WV-KY-OH metropolitan statistical area.