Japanization is the process in which Japanese culture dominates, assimilates, or influences other cultures, in general. According to The American Heritage Dictionary of the English Language, the word Japanize means To make or become Japanese in form, idiom, style, or character.

Narrowly, Japanization is referred as the "Tennoization" (皇民化; kōminka) during the imperial period (1868–1945). "Tennoization" is considered as the Japanese version of "Nazification" (Germanization from 1933 to 1945). During the imperial period, Japanese culture was forced into the submission to Tenno, including colonies and occupied territories.

During pre-imperial (pre-1868) period a peaceful diplomacy was practiced during which Japan did not expand much in territories beyond its own islands.

By the Meiji Restoration in 1868, the Empire of Japan was founded, Japan began its expansion in Asia and Oceania. Japanization of the imperial period was the "submission to Tenno", it was also practised in these newly conquered territories with different levels of intensity. It ended by the end of the World War II in 1945.