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 . It serves primarily as an alternate, inland route to National Route 45 through the northeastern part of the TÃ Âhoku region.
National Route 340 has a total length of .
National Route 340 was established by the Cabinet of Japan in 1975 between Rikuzentaka and Hachinohe.
All junctions listed are at-grade intersections unless noted otherwise.