The Haijin (海禁) or sea ban was a series of related policies in China restricting private maritime trading during much of the Ming dynasty and early Qing dynasty. The sea ban was an anomaly in Chinese history as such restrictions were unknown during other eras;the bans were each introduced for specific circumstances, rather than based on an age-old inward orientation.
In the first sea ban introduced in 1371 by the Ming founder Zhu Yuanzhang, Ming China's legal foreign trade was limited to tribute missions, placing international trade under a government monopoly. Initially imposed to deal with Japanese piracy amid anti-Ming insurgency, the Ming was not able to enforce the policy, and trade continued in forms such as smuggling. The sea ban was counterproductive: smuggling and piracy became endemic periodically (though not continuously), mostly perpetrated by Chinese who had been dispossessed by the policy. Piracy dropped to negligible levels upon the end of the policy in 1567. The policy slowed the growth of China's domestic trade, although the empire's weak enforcement of the policy opened the way for an unprecedented commercial revolution from the mid-1500s onward.