Nishio Tadamitsu (西尾 忠需, 1716 – April 25, 1760) was a daimyō in mid-Edo period Japan, who ruled Yokosuka Domain in Tōtōmi Province.Tadamitsu was the second son of Kyōgoku Takatoyo, daimyō of Marugame Domain in Sanuki Province. As Nishio Tadanao, had no heirs, he adopted his nephew in 1729. In 1731, Tadamitsu received the courtesy title of Mondo no Shō (主水正) along with junior 5th court rank, lower grade (ju go i no ge 従五位下).