The Dayton District is a railroad line owned and operated by the Norfolk Southern Railway in the U.S. state of Ohio.

The line runs from Columbus southwest to Cincinnati along former Pennsylvania Railroad and New York Central Railroad lines.

Its east end is at or near the Columbus District, Sandusky District, and West Virginia Secondary; its south end is in Ivorydale, where it meets the Indiana and Ohio Railway's Midland Subdivision, and just past that in Winton Place, where it meets CSX Transportation's Cincinnati Terminal Subdivision.

The two companies merged to form Penn Central Transportation in 1968 and were taken over by Conrail in 1976.

What was then known as the Cincinnati Line[6] was assigned to Norfolk Southern in the 1999 breakup of Conrail.