National Route 20 (国道20号, Kokudō nijū-gō) is a national highway connecting Tokyo and Shiojiri, Nagano prefecture in Japan. Originating at Nihonbashi in Chūō, Tokyo, it passes through Shinjuku and four other wards, and then seven cities, including Hachiōji in Tokyo. It follows a westward route into Kanagawa Prefecture, passing through the city of Sagamihara and one town. Continuing into Yamanashi Prefecture, the highway passes through nine cities and towns, among them the prefectural capital of Kofu. In Nagano Prefecture, National Route 20 passes through five cities and towns before entering Shiojiri, where it terminates at the intersection of National Routes 19 and 153. The highway is 225.0 km long.^[2]

National Route 20
国道20号
Route information
Length	225.0 km[1] (139.8 mi)
Existed	4 December 1952–present
Major junctions
South end	National Route 1 / National Route 4 / National Route 6 / National Route 14 / National Route 15 / National Route 17 in Nihonbashi, Chūō, Tokyo
North end	National Route 19 / National Route 153 in Shiojiri, Nagano
Location
Country	Japan
Major cities	Hachiōji Kofu
Highway system
National highways of Japan Expressways of Japan
← National Route 19 → National Route 21

National Route 20 is the successor to the Kōshū Kaidō, an Edo period highway connecting the shogunal capital of Edo and Kofu, then the principal city in Kai Province (or Kōshū, as it was also known). Parts of it still bear the old name.

The highway's course passes the Sakurada Gate of the Tokyo Imperial Palace. Shinjuku Station is on National Route 20. The marathon course of the Tokyo Olympics included parts of National Route 20.