Mizuno Tadakuni (水野 忠邦, July 19, 1794 – March 12, 1851) was a daimyō during late-Edo period Japan, who later served as chief senior councilor (Rōjū) in service to the Tokugawa shogunate.

As Rōjū Mizuno Tadakuni wielded tremendous political power, and attempted to overhaul the shogunate's finances and social controls in the aftermath of the Great Tempo Famine of 1832–36 by the passage of numerous sumptuary laws which came to be known as the Tenpō Reforms.

The reforms tried to stabilize the economy through a return to the frugality, simplicity and discipline that were characteristic from the early Edo period by banning most forms of entertainment and displays of wealth.

Another part of the Reform included the Agechi-rei which was to have daimyō in the vicinity of Edo and Ōsaka surrender their holdings for equal amounts of land elsewhere, thereby consolidating Tokugawa control over these strategically vital areas.

The general failure of the reforms caused Tadakuni to lose favor, and opinion of him declined further when Edo Castle burned down in May 1844.