The Battle of Cynthiana, or more specifically the Second Battle of Cynthiana or the Battle of Kellar's Bridge, included three separate engagements during the American Civil War that were fought on June 11 and 12, 1864, in Harrison County, Kentucky, in and near the town of Cynthiana. This was part of Confederate Brigadier General John H. Morgan's 1864 Raid into Kentucky. The battle ultimately resulted in a victory by Union forces over the raiders and ended Morgan's Last Kentucky Raid in defeat. Morgan's command had previously captured the town in the First Battle of Cynthiana, July 17, 1862.

Harrison County is a county located in the U.S. state of Kentucky. As of the 2020 census, the population was 18,692. Its county seat is Cynthiana. The county was founded in 1793 and named for Colonel Benjamin Harrison, an advocate for Kentucky statehood, framer of the Kentucky Constitution, and Kentucky legislator.