Nishio Naonori served as a bushō during the Sengoku period.
Naonori was born as the son of Nishio Hironori. He held the title of Assistant Director of the Bureau of Military Storehouses.
Based on a letter addressed to the Tōdai Temple manor regarding annual land taxes, Naonori is surmised to have been active from around 1486. In 1495, he informed Saitō Myōjun of the rebellion of Ishimaru Toshimitsu. Through the mediation of Toki Shigeyori, the mlitary governor of Mino, the two sides settled but Naonari was expelled to Owari Province based on allegations of slander. After the Battle of Funada which ended in the sixth month of 1496, Naonaori participated in an expedition by Myōjun to Ōmi Province, but encountered a local uprising and was killed along with Myōjun and Myōjun’s eldest son, Saitō Toshichika.
Naonori’s son, Nishio Hidenori, continued to serve the Saitō clan, but his relationship to Nishio Mitsunori is uncertain.