Long Branch is a stream in Boone, Audrain and Monroe counties of the U.S. state of Missouri. It is a tributary of the Salt River within the waters of Mark Twain Lake.
The stream source is in northeast Boone County about 1.5 miles west of Centralia at . The stream flows generally north through western Audrain County and into southwestern Monroe County just west of the community of Tulip. The stream turns east and generally follows the Audrain-Monroe county line for approximately 17 miles. Then the stream turn north and passes west of Santa Fe for about 3.5 miles to its confluence with the Salt River, at .
Long Branch was so named on account of its relatively long length.