was an Edo period Japanese samurai, 2nd Niwa daimyà  of Shirakawa Domain and the 1st Niwa daimyà  of Nihonmatsu Domain in the Tà Âhoku region of Japan. He was the 2nd hereditary chieftain of the Niwa clan. His courtesy title was Saikyà Â-no-daifu, and his Court rank was Junior Fourth Rank, Lower Grade.
Mitsushige was the third son of Niwa Nagashige, daimyà  of Shirakawa Domain. His childhood name of Miyamatsu-maru (éÂÂ太éÂÂ). As both of his older brothers died in childhood, he was named heir in 1628. In 1634, he was received in formal audience by Shà Âgun Tokugawa Iemitsu, and received a kanji from Iemitsu's name, becoming Niwa Mitsushige, along with the courtesy title of Saikyà Â-no-suke and Junior Fifth Rank, Lower Grade. On his father's death in 1637, he became daimyà  of Shirakawa Domain. Five years later, in 1642, his court rank was raised to Junior Fourth Rank, Lower Grade.
In 1643, the Tokugawa shogunate ordered the Niwa clan to relocate to Nihonmatsu. Upon entering Nihonmatsu Castle in 1644, Mitsushige immediately embarked on a program to improve upon the roads and to rebuild the surrounding jà Âkamachi. Mitsushige was also noted as a patron of the arts, and especially favoured the Sekishà «-branch of the Japanese tea ceremony along with ikebana and Japanese calligraphy and instituted the Nihonmatsu Lantern Festival in 1664. He was also a painter, having been trained in the Kanà  school, using the pseudonym Gyokuhà  (çÂÂå³°). He also invited noted priests from Mount Kà Âya and Manpuku-ji to his domains to establish Buddhist temples. In 1658, he gained the additional courtesy title of chamberlain. He retired from public life in 1679, turning the domain over to his eldest son Niwa Nagatsugu. He died in 1701.