Nishio Tadanao (西尾 忠尚, 1689 – April 25, 1760) was a daimyō in mid-Edo period Japan, who ruled Yokosuka Domain in Tōtōmi Province.
He also served as an official within the administration of Tokugawa shogunate, rising through the ranks first as Sōshaban, Jisha-bugyō, Wakadoshiyori, and finally to the position of Rōjū.
Tadanao entered the service of the Tokugawa administration in the spring of 1732, with his appointment to the offices of Sōshaban and Jisha-bugyō.
Tadanao's official wife was a daughter of Kyōgoku Takatoyo, the daimyō of Marugame Domain in Sanuki province, but he had no son.
The Enshu-Yokosuka San-Kumano Taisai festival, still held every year during a week in April, was started by Tadanao, who spent much time in Edo and wished to bring something of its culture to Yokosuka.