Sakoku
Sakoku (鎖国) was a policy of isolationism.
Some scholars refer to this as kaikoku (海禁, maritime restrictions) to clarify that there were exceptions.
History
Beginning in 1639, sakoku was the preeminent economic policy of the Tokugawa shogunate. Trade was restricted tightly.
Immigration was also entirely forbidden, with the primary intention therein being the expulsion and execution of foreign missionaries.
In 1868, the shogunate was coerced into ending isolationism.