Sato Issai (?? ??, 14 November 1772 – 19 October 1859) was a famous Confucian scholar during the late Edo period from Iwamura-han, Mino No Kuni (currently ??? Iwamura-cho in Gifu Prefecture).
Adopted by the Hayashi clan of scholars, his teachings or stints as adviser had a deep impact on many figures of the last days of the shogunate such as the reformers Tsugaru Yukitsugu, Sakuma Shozan, the painter Watanabe Kazan, Yokoi Shonan, and Nakamura Masanao.