| Country: | JPN |
| Type: | National |
| Route: | 420 |
| Map Custom: | yes |
| Length Km: | 66.5 |
| Length Ref: | [1] |
| Direction A: | West |
| Terminus A: | in Toyota, Aichi |
| Direction B: | East |
| Terminus B: | in Shinshiro, Aichi |
| Previous Type: | Route |
| Previous Route: | 419 |
| Next Type: | Route |
| Next Route: | 421 |
National Route 420 is a national highway of Japan connecting Toyota, Aichi and Shinshiro, Aichi in Japan, with a total length of 66.5 km (41.32 mi).