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.
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).
Tadamitsu became head of the Nishio clan in 1760, on Tadanao's death, and was appointed Sōshaban (master of ceremonies) in the administration of the Tokugawa shogunate.
His grave is located at the Nishio clan temple of Ryumin-ji in modern Kakegawa, Shizuoka.