Tokugawa Ieshige
was the 4th Matsudaira "daimyō" of Matsumoto Domain and 9th hereditary chieftain of the Toda-Matsudaira clan. Mitsumasa was the sixth son of Matsudaira Mitsuo and was posthumously adopted as heir to his brother, Matsudaira Mitsuyasu. He was received in formal audience by Shōgun Tokugawa Ieshige in 1759, and was appointed a "sōshaban" in 1767, holding that post until 1772. He retired in 1774 and was given the courtesy title of "Ise-no-kami". He died the following year. His wife was a daughter of Matsudaira Takechika of Tanagura Domain; however, he had no male heir.