Nishio Tadanari (西尾 忠成, 1653 – November 30, 1713) was a daimyō of the early to mid Edo period, Japan, who ruled the Tanaka and Komoro domains, and was finally transferred to Yokosuka Domain in Tōtōmi Province, where his descendants ruled until the Meiji Restoration.
However, as Tadaakira died in 1654, Tadanari succeeded to the Nishio clan leadership as an infant.
In 1661 the young Tadanari was received by shōgun Tokugawa Ietsuna, and given the courtesy title of Oki no kami and junior 5th court rank, lower grade.
Tadanari made great efforts to fix the damage caused by the misgovernment of Sakai Tadayoshi, the previous lord of Komoro; however, he was transferred once more (after barely three years in Shinano) to Yokosuka Domain.
However, administering the domain became a great burden, especially after the major earthquake of 1707, and he chose to retire, yielding clan headship to his son, Tadanao, in the summer of 1713.