Gennin (818 - December 14, 887) was a priest of the Shingon sect early in the Heian period. His exact origin is not known. He was also called Ikegami no Sozu, Nanchiin Sozu and Joganji Sozu.
He learned Hosso kyogaku (the dharmalogy of the Hosso study) under Gomyo and studied Esoteric Buddhism under Jichie, and his kanjo (a ceremony to be the successor) was held by Shinga and Shuei. In 878, he was appointed as naikubu-juzenshi (the 10 selected excellent priests for a Buddhist service in the Imperial Court), and in 883 was appointed as Gon no Risshi (a provisional rank in the lowest managerial position); then, in 885 he became Shosozu (junior secondary prelate) and the second manager of To-ji Temple. Famed for his abilities as a scholar, he established Nanchi-in Jogan-ji Temple and taught religious doctrine. His disciples, Yakushin and Shobo, opened the Hirosawa school and Ono school, respectively, and eventually the Tomitsu (eastern esotericism) was divided into these two schools.