| Country: | JPN |
| Type: | National |
| Route: | 166 |
| Map Custom: | yes |
| Length Km: | 125.4 |
| Length Ref: | [1] |
| Established: | 18 May 1953 |
| Direction A: | West |
| Terminus A: | in Habikino, Osaka |
| Direction B: | East |
| Terminus B: | in Matsusaka, Mie |
| Previous Type: | Route |
| Previous Route: | 165 |
| Next Type: | Route |
| Next Route: | 167 |
National Route 166 is a national highway of Japan connecting Habikino, Osaka and Matsusaka, Mie in Japan, with a total length of 125.4 km (77.92 mi).