Arnold Line is an unincorporated area and census-designated place (CDP) in Lamar County, Mississippi, United States.

It is in the northeast part of Lamar County and is bordered to the north, east, and south by the city of Hattiesburg.

The center of Hattiesburg is 5 miles (8 km) to the east in Forrest County.

West Hattiesburg is 1 mile (1.6 km) to the south of Arnold Line.

This Lamar County, Mississippi state location article is a stub.