Buan (c. 764 - October 15, 840) was a priest of the Ritsu sect during the early Heian period. He was from Mikawa Province.
After entering Toshodai-ji Temple, Buan completed his study of the precepts of Buddhism under Nyoho, who was a disciple of Ganjin (Jianzhen). After the death of his mentor Nyoho in 815, he succeeded as the fifth at Toshodai-ji-Temple and was named Risshi (the third rank of priest following Sojo and Sozu) in the following year in 816. Buan handed down Bosatsu-kai (Bodhisattva Precepts) to Emperor Heijo and in 827, and was promoted to Shosozu (a junior prelate). In 830, as a representative of Ritsu sect, Buan presented to Emperor Junna three volumes of 'Kairitsu Denrai Shushi Mondo' (Questions and answers about the precepts of Buddhism). When Saicho asked for the establishment of Kaidan (Buddhist ordination platform) in Enryaku-ji Temple, Buan together with Gomyo of Gango-ji Temple publicly opposed it. When Shio-in was built in Enryaku-ji Temple in 838, Buan worked as doshi (leader) there. In 835, he was promoted to Daisozu (the upper Buddhist priests in the second highest position). According to one theory, he passed away when he was 77 years old and was posthumously conferred sojo (a priest ranked in the highest managerial position).