South Dakota Highway 115 (SD 115) is a 40-mile (64 km) state highway in Lincoln and Minnehaha counties in South Dakota, United States, that was created from the routing of US 77, "Old 77", when its alignment was moved west to become Interstate 29 around 1980 and SD 15's route from US 18 to Sioux Falls.

South Dakota Highway 115 begins at an intersection with US 18 west of Canton and heads due north through rural Lincoln County.

The highway runs just east of Worthing and about a mile west of Harrisburg, South Dakota.

It runs along Minnesota Avenue in the southern portion of Sioux Falls and enters Minnehaha County upon crossing 57th Street.

[1] North of Sioux Falls, SD 115 travels through rural, sparsely populated areas of Minnehaha County.