Route 115 is a highway in the St. Louis, Missouri area. Its eastern terminus is at Interstate 70 (at Exit 248A) in St. Louis; its western terminus is also at I-70 (at Exit 237) in Berkeley near Lambert-St. Louis International Airport. The road is locally known as Natural Bridge Road, Natural Bridge Avenue, and Salisbury Street. It is one of two Missouri Highways that are odd designations, but run east–west.

Beginning in St. Louis as Salisbury Street, a narrow neighborhood commercial street:

Turns slightly northwest to become the six-lane-wide Natural Bridge Avenue:

Enters St. Louis County at 6100 block, name changes to Natural Bridge Road:

Divided highway begins. From west of I-170 to west of Brown Road, a number of commercial buildings are located in the divider in the middle of the roadway.

West of I-70 exit 237, the name Natural Bridge Road continues westward as an I-70 south outer road for several miles. Prior to the construction of I-70 and several phases of expansion of Lambert Airport, Route 115 continued west into St. Charles, Missouri. This route included a road called Natural Bridge Road in Bridgeton, Missouri which has been significantly impacted by recent airport expansion. Part of St. Charles Rock Road west of I-270 was also part of Route 115, as was the bridge across the Missouri River into St. Charles.

After the Discovery Bridge on the eastern portion of Route 370 opened in 1992, the portions of Route 115 west of Lambert Airport were deleted. The Natural Bridge portion became Route B; the St. Charles Rock Road portion became Route A. In 1998, the former Route 115 bridge across the Missouri River was demolished.