Highway 45 (AR 45, Ark. 45, or Hwy. 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.

The route begins at Highway 96 in Hartford and runs north to form a concurrency with Highway 252 through Midland. Further north, the route has an Officially designated exception of 0.45 miles (0.72 km) through downtown Hackett. Slightly north of this exception, Highway 45 runs on the Hackett Creek Bridge and continues north to Bonanza. The route intersects Highway 253 and curves east to form a concurrency with US 71. The highway splits from US 71 to the north and, entering Fort Smith and intersecting Highway 255 before terminating at I-540/US 71.

Highway 45 begins at Highway 59 at the incorporated community of Dutch Mills, and runs east past the Bethlehem Cemetery and Twin Bridges Historic District, both on the National Register of Historic Places. The route continues northeast through Clyde before passing the Pyeatte Mill Site and entering the historic community of Canehill. Continuing north, the highway meets US 62 east of Lincoln, where it terminates.

The third routing of Highway 45 begins at US 71B and runs west as Lafayette Street through Fayetteville. Highway 45 runs through the Washington-Willow Historic District before a sharp left turn onto Mission Boulevard. The highway continues northeast until intersecting Highway 265 and exiting Fayetteville heading east. Passing the Son's Chapel and entering Goshen, the highway continues east through rural Washington County until entering Madison County shortly after a junction with Highway 303. Highway 45 has a junction with Highway 295 before forming a concurrency with US 412 Business north through Hindsville. The route continues north, with US 412B terminating at a junction with US 412 and Highway 45 terminating at Highway 12 near Clifty.

Arkansas Highway 45 was one of the original 1926 state highways. The route ran north from Oklahoma west of Hartford, Arkansas to Clifty. The middle segment was replaced by Arkansas Highway 59 between Van Buren and Dutch Mills, and the route remains fragmented today.

County	Location	mi	km	Destinations	Notes
Sebastian	Hartford	0.00	0.00	AR 96 – Mansfield, Hartford, Monroe, OK
	​	4.00	6.44	AR 252 east – Huntington	South end of AR 252 overlap
	Midland	5.51	8.87	AR 253 north (Third Street) – Excelsior
	​	6.82	10.98	AR 252 west – Slaytonville	North end of AR 252 overlap
	Hackett	13.81	22.23	AR 10 west	South end of AR 10 overlap
		14.26	22.95	AR 10 east – Greenwood	North end of AR 10 overlap
	Enterprise	19.71	31.72	AR 253 north
	Fort Smith	23.07	37.13	US 71 south – Greenwood	South end of US 71 overlap
		0.00	0.00	US 71 north – Fort Smith	North end of US 71 overlap
		3.02	4.86	AR 255 (Zero Street) to I-540 – Downtown Fort Smith, Barling
		3.90	6.28	I-540 (US 71) to I-40 – Spiro, OK, Van Buren	I-540 exit 10
Gap in route
Washington	​	0.00	0.00	AR 59 to US 62 – Van Buren
	​	10.64	17.12	US 62 – Lincoln, Prairie Grove
	Gap in route
	Fayetteville	0.00	0.00	College Avenue	Former US 71B
				Assembly Road - Mount Sequoyah Assembly	Former AR 180 east
		2.88	4.63	AR 265 (Crossover Road) to AR 16 – Springdale
	​			CR 345 (Gulley Road)	Former AR 156 west
	Mayfield	14.41	23.19	AR 303 north – Spring Valley
Madison	​	16.83	27.09	AR 295
	​	19.32	31.09	US 412B east to US 412 east – Huntsville	South end of US 412B overlap
	​	0.00	0.00	US 412 – Springdale, Huntsville	North end of US 412B overlap
	​	6.10	9.82	AR 12 – Rogers, Clifty, Eureka Springs
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus

• List of state highways in Arkansas

Media related to Arkansas Highway 45 at Wikimedia Commons