Highway 43 (AR 43, Ark. 43, and Hwy. 43) is a designation for three north–south state highways in northwest Arkansas. One segment of 27.1 miles (43.6 km) runs from Highway 59 in Siloam Springs north into Delaware County, Oklahoma along Oklahoma State Highway 20 (SH-20) to terminate at Missouri Route 43 (Route 43) at the Missouri/Oklahoma/Arkansas tri-point near Southwest City, Missouri. A second segment of 20.0 miles (32.2 km) runs northeast from Highway 21 at Boxley to Highway 7 in Harrison. The third segment runs 1.8 miles (2.9 km) north in Harrison from US Route 65 (US 65) to Highway 7 .

The route begins at AR 59 in Siloam Springs and runs west to intersect AR 264. The route continues west before turning north and running close to the Oklahoma state line. AR 43 runs through Cherokee City before meeting AR 102 and later AR 72 in Maysville.

After Maysville, AR 43 runs along the Oklahoma state line concurrent with Oklahoma State Highway 20. This continues for approximately 5.4 miles (8.7 km) until both routes terminate at Missouri Route 43.

In an almost-as-unique situation, for the northernmost few miles of the overlapping stretch of road AR 43/SH 20 turns toward the west, no longer straddling the state line. For those few miles, Highway 43 is located wholly within the state of Oklahoma but is not apparent to the traveler.

AR 43 is famous among roadgeeks for its concurrency with Oklahoma State Highway 20. This is possibly the only example of state highways from two different states concurring in the United States.

AR 43 begins at Highway 21 at Boxley, and runs north near the Buffalo National River. The route enters Boone County and serves as the western terminus of AR 206, and the southern terminus of AR 397. AR 43 terminates at AR 7 in south Harrison. The route runs for 15.9 miles (25.6 km) in Newton County and 14.1 miles (22.7 km) in Boone County.

The route begins at U.S. Route 65 on the north end of Harrison and runs east to AR 7 north of Harrison.

Originally numbered AR 99, the route was renumbered in the mid-1960s to its present number. AR 99's southern terminus was originally at U.S. Route 412 in Siloam Springs, but was rerouted in the mid-1990s along the former AR 204, terminating at Highway 59.

Arkansas Highway 43 Spur was a spur route of 1.0 mile (1.6 km) in Siloam Springs. It was decommissioned when AR 43 was rerouted along AR 204.