The jōkamachi (城下町, lit. 'castle city') were centres of the domains of the feudal lords in medieval Japan. The jōkamachi represented the new, concentrated military power of the daimyo in which the formerly decentralized defence resources were concentrated around a single, central citadel. These cities did not necessarily form around castles after the Edo period; some are known as jin'yamachi, cities that have evolved around jin'ya or government offices that are not intended to provide military services. Defined broadly, jokamachi includes jin'yamachi. It is also referred to as jōka, as was common before the early modern period.

The origins of jōkamachi dates back to the Kamakura period, but it was not until the 1570s in the Sengoku period that the jōkamachi predominated other types of town.

The jōkamachi can be divided into the shugo jōkamachi, in which a castle town is ruled by the resident daimyo. While the shugo jōkamachi were the political centres of the domain, economic activities were greater in the towns that developed around shrines and temples (monzen machi) and port towns (minato machi). In the midl-16th century, the castle towns proliferated and became both the residence of the daimyo and the political centre of the domain (sengoku jōkamachi).

Jōkamachi functions both as a military base represented by the castle and an administrative and commercial city. Oda Nobunaga was the biggest contributor to the development of early-modern jōkamachi. Oda aimed at promoting the heinobunri (distinguishing the samurai class from the rest by giving privileged status to samurai and disarming farmers and the rest) by forcing the samurai class to live in jōkamachi, while establishing rakuichi-rakuza (free markets and open guilds) to stimulate merchandising and trade. Jōkamachi flourished even more under Toyotomi Hideyoshi's regime, whose political and commercial epicenter Osaka-jōka became very prosperous as the center of commodities. Osaka continued to be the business center in the Edo period and was called the "kitchen of the land".

Most of the world's walled cities comprise a castle and a city inside the defensive walls. While Japan did have towns and villages surrounded by moats and earth mounds, such as Sakai, jōkamachi initially had moats and walls only around the feudal lord's castle and did not build walls around the entire city. However, as jōkamachi developed and increased its economic and political value, it demanded protection from wars and turmoil. More and more cities were built with moats and defensive walls, the style of which is known as so-gamae (full defence perimeter), and gradually came to resemble walled cities.

In the Edo period, jōkamachi served less as a military base and more as a political and economic capital for the shogunate government and domains of feudal lords. This shift was a result of the lack of warfare throughout the Edo period and the fact that most of the Han lords were occasionally transferred from one domain to another and thus had little attachment to the city per se (although crop yields remained matters of attention). Geographical locations that emphasized the castle's defensive abilities did not necessarily offer good access, and in many cases, as cities increasingly became trade centers, they abandoned their castles and relocated their government base in Jin'ya.

The population of a jōkamachi, of which nearly 300 existed, is varied. There are large-sized jōkamachi such as Kanazawa and Sendai with approximately 120,000 residents, samurai and merchants combined, while there are small-sized jōkamachi like Kameda in the Tohoku area with around 4,000 people. In many cases, the population is somewhere around 10,000.

The design of a jōkamachi aimed to stimulate commerce by reworking the closest main road to pass through the city so that traffic occurs within the jōka. The main road passed through the front of the castle rather than the back to demonstrate the power of the authority, regardless of geographical concerns that might exist.