| State: | CT |
| Type: | CT |
| Route: | 121 |
| Map Custom: | yes |
| Map Notes: | Map of New Haven County in southern Connecticut with Route 121 highlighted in red |
| Length Mi: | 5.66 |
| Length Round: | 2 |
| Length Ref: | [1] |
| Established: | 1932 |
| Direction A: | South |
| Terminus A: | in Milford |
| Junction: | in Orange |
| Direction B: | North |
| Terminus B: | in Orange |
| Counties: | New Haven |
| Previous Type: | Route |
| Previous Route: | 120 |
| Next Type: | Route |
| Next Route: | 122 |
Route 121 is a state highway in southern Connecticut running from U.S. Route 1 in Milford to Route 34 near the Orange-Derby line.
Route 121 begins at an intersection with US 1 in Milford and heads north, passing underneath I-95 without a junction 0.3miles later, then enters the town of Orange after another 1.5miles. In Orange, Route 121 continues north, intersecting about half a mile later with Derby-Milford Road, a direct route into Derby, and the Wilbur Cross Parkway (Route 15) at Exit 56 after another 1.6miles. The road continues past the Wilbur Cross Parkway for another 1.6miles until the intersection with Route 34 (Derby Turnpike) in the northern edge of Orange, where Route 121 ends. In Milford, Route 121 is known as North Street, while in Orange, it is known as Grassy Hill Road.[1]
In the 1920s, the current alignment of Route 121 was known as State Highway 195 and was one of the routes between Milford and Derby. In the 1932 state highway renumbering, old Highway 195 became Route 121. In 1941, Route 121 was shortened when US 1 was relocated from Cherry Street to its current route at the Boston Post Road. North Street south of current Route 1 is still signed as the route for the Milford train station.[2] [3]