Niwa Nagatomi (????, October 12, 1803 – August 12, 1866) was an Edo period Japanese samurai, and the 9th daimyo of Nihonmatsu Domain in the Tohoku region of Japan.
He was the 10th hereditary chieftain of the Niwa clan.
His courtesy title was Saikyo-no-daifu, and his Court rank was Junior Fourth Rank, Lower Grade.