Hardin county is in the Pennyrile region of Kentucky. The elevation in the county ranges from 383 to 1017 feet above sea level.
It was formed in 1793 from Nelson county. Hardin county was a source of Ohio (1799), Breckinridge (1800), Grayson (1810), Hart (1819), Meade (1824), and LaRue (1843) counties. The county seat is Elizabethtown.
In 2010 the county population was 105,543 in a land area of 623.28 square miles, an average of 169.3 people per square mile.
The equine population was 4,300 in the 2012 Kentucky Equine Survey.
Hardin county was named for Colonel John Hardin, who fought in the American Revolution and was killed in 1792 while leading an expedition to negotiate with the Shawnee in Ohio.
Part of Fort Knox is in the county.