The Kansei Reforms were a series of reactionary policy changes and edicts which were intended to cure a range of perceived problems which had developed in mid-18th-century Tokugawa Japan. Kansei refers to the nengō that spanned the years from 1789 through 1801; with the reforms occurring during the Kansei period but between the years 1787–1793. In the end, the shogunate's interventions were only partly successful. Intervening factors like famine, floods and other disasters exacerbated some of the conditions which the shōgun intended to ameliorate.

Matsudaira Sadanobu (1759–1829) was named the shōgun's chief councilor (rōjū) in the summer of 1787; and early in the next year, he became the regent for the 11th shōgun, Tokugawa Ienari. As the chief administrative decision-maker in the bakufu hierarchy, he was in a position to effect radical change; and his initial actions represented an aggressive break with the recent past. Sadanobu's efforts were focused on strengthening the government by reversing many of the policies and practices which had become commonplace under the regime of the previous shōgun, Tokugawa Ieharu. Sadanobu increased the bakufu's rice reserves and required daimyos to do the same. He reduced expenditures in cities, set aside reserves for future famines, and encouraged peasants in cities to go back to the countryside. He tried to institute policies that promoted morality and frugality, such as prohibiting extravagant activities in the countryside and curbing unlicensed prostitution in the cities. Sadanobu also cancelled some debts owed by daimyos to the merchants.

These reform policies could be interpreted as a reactionary response to the excesses of his rōjū predecessor, Tanuma Okitsugu (1719–1788). The result was that the Tanuma-initiated, liberalizing reforms within the bakufu and the relaxation of sakoku (Japan's "closed-door" policy of strict control of foreign merchants) were reversed or blocked. Education policy was changed through the Kansei Edict of 1790 which enforced teaching of the Neo-Confucianism of Zhu Xi as the official Confucian philosophy of Japan. The decree banned certain publications and enjoined strict observance of Neo-Confucian doctrine, especially with regard to the curriculum of the official Hayashi school.

This reform movement was related to three others during the Edo period: the Kyōhō reforms (1722–30), the Tenpō reforms of 1841–43 and the Keiō reforms (1864–67).