Junsai (year of birth unknown - March 16, 1207) was a priest of the Jodo (Pure Land) sect of Buddhism who lived from the late Heian period to the early Kamakura period
His father was NAKAHARA no Morohide. His bomyo (another name of a priest) was Anrakubo (he was also referred to as Anraku from this bomyo). His secular name was NAKAHARA no Morohiro.
At first he served TAKASHINA no Yasutsune, Okura-kyo (Minister of the Treasury), but later studied under Honen (founder of the Jodo sect) after becoming a priest. In 1192 when Honen, at the wish of a Buddhist priest named Hachido Kenbutsu of the Yamato Province, dedicated Betsuji nenbutsu (practices in which ascetics chant the name of the Buddha and give invocation of the Buddha's name on a fixed date and time) at the Yasaka Indo-ji Temple, Junsai, together with his fellow priest Juren, was engaged in devotional exercises of Rokuji raisan (devotional exercises where Buddhist priests pray to the Buddha at six in the morning and the evening). In 1198 when Honen compiled Senchaku Hongan Nenbutsu Shu (the holy writings of the Jodo sect), Junsai was ordered to write it. Blessed with musical talent, he had followers of the nenbutsu chant the Rokuji raisan in a chorus to a tune he had written with his fellow priest Juren, and thus he played a vital role in spreading Senju Nenbutsu (the Single-Minded Recitation of the Nenbutsu). Under suspicion that he committed adultery with court ladies who were serving Emperor Gotoba, he was executed by decapitation along with his disciple priests at the riverbank of Rokujo-gawara in 1207. It is well known that prior to his funshu (decapitation) punishment, his penis was cut off. This incident directly triggered Jogen no Honan (an event where four apprentices of Honen were executed and seven others including Honen and Shinran were banished by Retired Emperor Gotoba) for which Honen was exiled to Oki Island and Shinran to the Echigo Province.