Highway 45 is a designation for three state highways in northwest Arkansas. The southern segment of 26.97 miles (43.40 km) runs from Highway 96 north across US Route 71 (US 71) to Interstate 540/US 71 (I-540/US 71) in Fort Smith. Another segment of 10.64 miles (17.12 km) runs Highway 59 at Dutch Mills to US 62 in rural Washington County. A third route of 25.42 miles (40.91 km) runs from U.S. Route 71B (US 71B) in Fayetteville to Highway 12 near Clifty. These routes were formerly connected until a portion of approximately 50 miles (80 km) was redesignated Arkansas Highway 59 and many United States highways were rerouted through Fayetteville.

U.S. Highway 71 is a U.S. highway that runs from Krotz Springs, LA to the Fort Frances–International Falls International Bridge at the Canadian border. In Arkansas, the highway runs from the Louisiana state line near Doddridge to the Missouri state line near Bella Vista. In Texarkana, the highway runs along State Line Avenue with US 59 and partially runs in Texas. Other areas served by the highway include Fort Smith and Northwest Arkansas.