| State: | AR |
| Type: | AR |
| Route: | 121 |
| Map: | Arkansas 121.png |
| Length Mi1: | 9.49 |
| Length Round: | 2 |
| Length Ref1: | [1] |
| Direction A1: | South |
| Terminus A1: | at the St. Francis River |
| Direction B1: | North |
| Terminus B1: | near Marianna |
| Length Mi2: | 29.92 |
| Direction A2: | North |
| Terminus A2: | near Marianna |
| Direction B2: | South |
| Terminus B2: | Young Boulevard, LaGrange |
| Counties: | Lee |
| Previous Type: | AR |
| Previous Route: | 120 |
| Next Type: | AR |
| Next Route: | 122 |
Arkansas Highway 121 (AR 121, Hwy. 121) is a designation for two state highways in Lee County, Arkansas. One route of 9.49miles runs from the St. Francis River to US Route 79 (US 79) northeast of Marianna.[2] A second routing begins north of Marianna at Highway 1 and runs essentially in a half-loop counterclockwise to LaGrange.
Highway 122 begins at Lee County Route 513 at the shore of the St. Francis River about 4miles west of the Mississippi River. The highway winds northwest through floodplain to terminate at US 79, which is designated as part of the Great River Road.
The second portion of Highway 121 begins at Highway 1 north of Marianna and runs west through farmland. Highway 121 has a junction with Highway 261 at Holub, after which Highway 121 turns due south. The route continues south to US 79 at Smith Corner when the two routes overlap for approximately 0.5miles at which time Highway 121 turns south again.
After running south through a few miles of farmland the route enters Aubrey as Main Street and intersects Highway 78.[3] At Big Creek Corner the route curves east after a junction with Highway 243. Now entering Rondo the route has junction with Highway 243 (Main Street) and serves as the western terminus for Highway 316.[4] The route continues approximately 5miles further east to intersect Highway 1 before it terminates at Young Boulevard in LaGrange.[5]
Traffic counts from the Arkansas State Highway and Transportation Department (AHTD) reveal that less than 200 vehicles per day (VPD) used Highway 121 from the St. Francis River to US 79 in 2010. The semi-circular rural portion from Highway 1 to LaGrange varies between 350–950 VPD.
Mile markers reset at concurrencies.