Cai Yi 蔡義 (died 71 BCE), also called Cai Yi 蔡誼, was a high official of the mid-Former Han period 前漢 (206 BCE-8 CE).
He hailed from Henei 河內 (modern Mengxian 孟縣, Henan) and was a Confucian retainer of the powerful general Huo Guang 霍光. He continued living a simple life of austerity and later earned his money as a gate keeper. Emperor Zhao 漢昭帝 (r. 87-74 BCE) once sought for scholars proficient in the Han exegesis of the Shijing 詩經 "Book of Songs", and so invited Cai Yi to the court.
Cai was appointed Grand Master of Splendid Happiness (guanglu dafu 光祿大夫), palace steward (jishizhong 給事中) and instructed the emperor in the "Songs". Shortly after he was promoted to Chamberlain for the Palace Revenues (shaofu 少府) and Censor-in-chief (yushi dafu 御史大夫).