| State: | AR |
| Type: | AR |
| Route: | 166 |
| Map: | Arkansas 166.png |
| Length Mi1: | 7.97 |
| Length Ref1: | [1] |
| Direction A1: | South |
| Terminus A1: | at Davidsonville Historic State Park |
| Direction B1: | North |
| Terminus B1: | in Pocahontas |
| Length Mi2: | 14.57 |
| Direction A2: | South |
| Terminus A2: | in Pocahontas |
| Direction B2: | North |
| Terminus B2: | at Missouri state line |
| Counties: | Randolph |
| Previous Type: | US |
| Previous Route: | 165 |
| Next Type: | US |
| Next Route: | 167 |
Arkansas Highway 166 is a designation for two state highways in Randolph County, Arkansas. The southern segment of 7.97miles runs from Old Davidsonville State Park to Pocahontas. A northern segment of 14.57miles runs north from US 62/US 67 to the Missouri state line.[2]
AR 166 begins at Davidsonville Historic State Park in southwest Randolph County. The route runs north to meet US Route 62 in south Pocahontas. The route is entirely two-lane, undivided.
AR 166 begins at US 62/US 67 (Future I-57) in east Pocahontas. The route runs north to meet AR 115 at Stokes and AR 328 in Maynard. AR 166 then trails north through Supply and Minorea to the Missouri state line, where it terminates at Missouri supplemental routes A/Y.
Mile markers reset at concurrencies.|-| align=center colspan=5 | concurrency north, 4.9miles|-