Mississippi Highway 43 generally runs north–south in three segments: the first from U.S. Highway 90 near Bay St. Louis to Mississippi Highway 13 south of Columbia, resuming at MS 13 in southern Jefferson Davis County to end near Mendenhall, and finally starting again at Mississippi Highway 18 near Puckett to end at Attala Road 3122 in northern Attala County. It traverses approximately 235 miles (378 km), serving Hancock, Pearl River, Marion, Jefferson Davis, Lawrence, Simpson, Rankin, Madison, Leake, and Attala counties.

From north to south

MS 43 Spur, officially inventoried as Mississippi Highway 992, is a short local road which runs through Picayune, Mississippi. Its northern terminus is at MS 43 and its southern terminus is just north of Goodyear Boulevard in Picayune.