Kentucky Route 3 originates at a junction with U.S. Highway 23 west of Prestonsburg in Floyd County, Kentucky, United States. The route continues through Johnson, Martin and Lawrence counties to terminate at another junction with U.S. Highway 23 south of Catlettsburg in Boyd County.

From South Catlettsburg to Louisa it follows the original routing of U.S. 23. It intersects KY-180, which parallels I-64, after 6.4 miles. At this intersection, you turn right to stay on KY-3. The road continues 8 miles to the Lawrence County line. In Lawrence County, it passes KY-1 and KY-1185, which takes you to Yatesville Lake. It then continues into downtown Louisa toward Inez and on to Prestonsburg.