Nishio Tadaatsu

Viscount Nishio Tadaatsu (西尾 忠篤?, June 16, 1850 – November 5, 1910) was the final daimyō of Yokosuka Domain in Tōtōmi Province in late-Edo period Japan, and the first (and only) daimyō of Hanabusa Domain in Awa Province in the early years of the Meiji period.

Tadaatsu was the son of Nishio Tadasaka, the 7th daimyō of Yokosuka Domain. His mother was a daughter of Toki Yorinobu, the daimyō of Numata Domain in Kōzuke Province. He became daimyō of Yokosuka and head of the Nishio clan upon his father's death in 1861.

During the Boshin War of the Meiji Restoration, Tadaatsu's retainers were divided as to whether or not the domain should continue to support the shogunate, or join forces with the Satchō Alliance in support of the new imperial government. Thanks to the persuasion of Yaso Tomiho and Aoyama Zen'ichirō, the pro-shogunate elements in Yokosuka dropped their objections, and the Yokosuka Domain peacefully submitted to the Imperial army. As a gesture of loyalty, Yokosuka Domain contributed forces to assisted the new government in its suppression of remaining pro-Tokugawa partisans in northern Japan. In 1868, due to Tokugawa Iesato's entry into the Tōkaidō region as daimyō of the newly created Sunpu Domain, Tadaatsu was transferred to Hanabusa Domain, in Awa Province. Tadaatsu ruled Hanabusa as daimyō until 1869, when he was made han chiji (domainal governor). He finally left Hanabusa after the abolition of the domains in 1871, and relocated to Tokyo. He was later created a viscount under the kazoku peerage system.

Tadaatsu was married to a daughter of Matsudaira Chikayoshi, daimyō of Kitsuki Domain in Chikugo Province, and had two daughters, but no male heir.

Tadaatsu died in 1910, at age 61. His grave is at the temple of Myogon-ji at Ageo, Saitama.