National Route 138 is a national highway of Japan connecting Fujiyoshida, Yamanashi and Odawara, Kanagawa in Japan, with a total length of 61.4 km (38.15 mi).

The highway connects Odawara in the western side of Kanagawa Prefecture to Fujiyoshida, a city on the northern side of Mount Fuji in Yamanashi Prefecture.

The highway travels through the northern portion of the park, exiting it at its northwestern corner.

It then travels across the city and then enters the neighboring town, Oyama.

It then hugs the southern shore of Lake Yamanaka, the largest of the Fuji Five Lakes before crossing into Fujiyoshida where it meets its western terminus at an intersection with National Route 137.