is both the southernmost and westernmost of the national highways of Japan. It connects Ishigaki, Okinawa on Ishigaki Island, to Miyako-jima, and Naha, Okinawa on Okinawa Island in Japan. Spanning the three islands by ferry, the highway has a total length of on land and when maritime distance is added.
National Route 390 features the 730 Intersection in Ishigaki, a monument to the day when traffic in Okinawa Prefecture was reverted from driving on the right-hand side of the road to the left after the United States relinquished control over the prefecture to Japan following the 1971 Okinawa Reversion Agreement.