Kaidō (街道, road^?) were ancient roads in Japan dating from the Edo period. Major examples include the Edo Five Routes, all of which started at Edo (modern-day Tokyo). Minor examples include sub-routes such as the Hokuriku Kaidō and the Nagasaki Kaidō.

Kaidō, however, do not include San'yōdō, San'indō, Nankaidō and Saikaidō, which were part of the even more ancient system of Yamato government called Gokishichidō. These names were used for administrative units, and the roads within these units.

Many highways and railway lines in modern Japan follow the ancient routes and carry the same names. The early roads radiated from the capital at Nara or Kyoto. Later, Edo was the reference, and even today Japan reckons directions and measures distances along its highways from Nihonbashi in Chūō, Tokyo.

The five main kaidō from Nihonbashi in Edo were:

At various times, the government established post stations (shukuba) along the roads. These had lodgings for travelers and grew as commercial centers. These former post towns, along with castle and harbor towns, form a major category of cities in Japan.