Mizuno Tadakiyo (水野 忠精, February 5, 1833 – May 8, 1884) was a daimyō during Bakumatsu period Japan, who served as chief senior councilor (Rōjū) in service to the Tokugawa shogunate.

After the failure of the Tenpō Reforms, Tadakuni was forced into retirement and exile, and turned the leadership of the Mizuno clan and the position of daimyō of Hamamatsu Domain to Tadakiyo in 1845.

Within the shogunal administration, he received the post of Jisha-bugyō (Commissioner of Shrine and Temples) and wakadoshiyori (Junior Councilor).

As Rōjū, he worked with Oguri Tadamasa in the construction of Yokosuka Naval Arsenal as part of the Tokugawa shogunate’s efforts to modernize Japan’s military.

He retired from public life in 1866 on the death of Shōgun Tokugawa Iemochi, and was succeeded at Yamagata by his son Mizuno Tadahiro.