What was the period of rapid modernization in Japan in the 1800's called?

The period of rapid modernization in Japan in the 1800s was called the Meiji Restoration.

Beginning in 1868, the Restoration ended the political dominance of the Tokugawa shogunate and formally restored imperial rule under Emperor Meiji. It launched sweeping changes to Japan’s government, economy, military, education system, and society.

Japan adopted many Western technologies and institutions while building railways, modern factories, a conscript army, and a centralized national government. The Meiji leadership pursued modernization partly to prevent Japan from suffering the fate of Asian countries threatened or controlled by Western imperial powers.

Strictly speaking, the Meiji Restoration describes the political transformation that began in 1868, while the Meiji era lasted from 1868 to 1912 and included the broader modernization process. In ordinary quiz usage, however, “Meiji Restoration” is the established answer to this question. The transition was not peaceful for everyone: former samurai and traditionalists resisted reforms, culminating in the Satsuma Rebellion of 1877.