South Dakota Highway 43 (SD 43) is a 1.131-mile-long (1.820 km) state highway that exists entirely in the southern part of Gregory County in the southern part of the U.S. state of South Dakota.

It travels northwest for just over 1 mile (1.6 km) before meeting its northern terminus at an intersection with US 18.

The highway does not travel through any populated areas, but rather serves as a connector route between N-11 and US 18.

The number was removed around 1940, when SD 50 was extended northwest from its previous terminus near Ravinia (east of Lake Andes).

That highway's entrance into South Dakota was moved about 9 miles (14 km) to the east, by 1962.