| Country: | JPN |
| Type: | National |
| Route: | 123 |
| Map Custom: | yes |
| Length Km: | 70.0 |
| Length Ref: | [1] |
| Established: | 1963 |
| Direction A: | West |
| Terminus A: | in Utsunomiya |
| Direction B: | East |
| Terminus B: | in Mito, Ibaraki |
| Previous Type: | Route |
| Previous Route: | 122 |
| Next Type: | Route |
| Next Route: | 124 |
National Route 123 is a national highway of Japan connecting Utsunomiya and Mito, Ibaraki in Japan, with a total length of 70 km (43.5 mi).
Route 123 was originally designated on 18 May 1953 from Chiba to Mito. This was redesignated Route 51 on 1 April 1963 and the current Route 123 was designated the same day.