South Portsmouth is an unincorporated community in Greenup County, Kentucky, United States. South Portsmouth is located on the Ohio River across from Portsmouth, Ohio and 3 miles (4.8 km) west of South Shore, Kentucky. Kentucky Route 8 passes through the community.
South Portsmouth was originally called Springville due to the numerous springs in the area. Springville was incorporated as a town on March 3, 1876. The Chesapeake and Ohio Railroad built a track through the community in the early 1900s. Subsequently the name of the community was changed to South Portsmouth, presumably to indicate its location and strengthen its connection with Portsmouth, Ohio, a city of more than 20,000 people.