| Country: | JPN |
| Type: | National |
| Route: | 121 |
| Map Custom: | yes |
| Length Km: | 249.6 |
| Length Ref: | [1] |
| Established: | 1953 |
| Direction A: | North |
| Terminus A: | in Yonezawa, Yamagata |
| Direction B: | South |
| Terminus B: | in Mashiko, Tochigi |
| Previous Type: | Route |
| Previous Route: | 120 |
| Next Type: | Route |
| Next Route: | 122 |
is a national highway connecting the city of Yonezawa, Yamagata and the town of Mashiko, Tochigi in Japan.