| Country: | JPN |
| Type: | National |
| Route: | 340 |
| Map Custom: | yes |
| Map Notes: | Japan National Route 340 highlighted in red |
| Length Km: | 246.2 |
| Length Ref: | [1] |
| Established: | 1 April 1975 |
| Direction A: | South |
| Terminus A: | in Rikuzentakata, Iwate |
| Direction B: | North |
| Terminus B: | in Hachinohe, Aomori |
| Previous Type: | Route |
| Previous Route: | 339 |
| Next Type: | Route |
| Next Route: | 341 |
is a national highway of Japan connecting the cities of Rikuzentakata, in southeastern Iwate Prefecture, and Hachinohe, in southeastern Aomori Prefecture. It travels south to north and has a total length of 246.2km (153miles). It serves primarily as an alternate, inland route to National Route 45 through the northeastern part of the Tōhoku region.
National Route 340 has a total length of 246.2km (153miles).
National Route 340 was established by the Cabinet of Japan in 1975 between Rikuzentaka and Hachinohe.[2]
All junctions listed are at-grade intersections unless noted otherwise.