Sakoku (Japanese 鎖国, literally "chained country") is a keyword which explains the foreign relations policy of the Tokugawa shogunate from 1641 to 1853 in the History of Japan. During this period, nobody, whether foreign or Japanese, could enter or leave Japan on pain of death. The one foreign influence permitted was the Dutch "factory" (trading post) at Dejima in Nagasaki.

The way Japan kept abreast of Western technology during this period was by studying medical and other texts in the Dutch language obtained through Dejima. This process was called "Rangaku" (Dutch studies). It became obsolete after the country was opened and the sakoku policy collapsed. Thereafter, many Japanese students (e.g. Kikuchi Dairoku) were sent to study in foreign countries, and many foreign employees were employed in Japan (see o-yatoi gaikokujin).