Joan (790 - March 25, 844) was a Hosso sect Buddhist monk during the early Heian period.
He studied the Hosso doctrine under Joto in Saidai-ji Temple in Nara and lived in Ganko-ji Temple. Later, he built a hermitage at the foot of Mt. Hira in Omi Province. In the hermitage, he read a sutra Butsumyokyo and led a penitential life. Joan first carried out the religious service 'Butsumyoe' in 838 and 'Kanbutsuse' in the Imperial Court, and thereafter, the services continued as annual events of the Imperial Court. Later, he founded Myoho-ji Temple and Saisho-ji Temple on Mt. Hira.