"Bodaisen" was a name-brand sake (Japanese rice wine) which had the reputation of having the highest quality and grade from the middle of the Heian period to the end of the Muromachi period.
Bodaisen was a kind of "soboshu" (monk's sake), brewed at Shoryaku-ji Temple on Mt. Bodai in Nara, using both the water of the Bodaisen-gawa River running through the temple precinct and "Bodai-moto" (the starter mash, or the sake brewing method using the mash), and it belonged to "Nanto moro-haku" (several kinds of soboshu having the highest quality).
There is a theory that Bodaisen was the first sake to be brewed in Japan, and a stone monument inscribed as such stands in the precinct of Shoryaku-ji Temple.
Bodaisen was in its prime in the early Muromachi period (in other words, the period of the Northern and Southern Courts), and after a while, from the Period of Warring States, it went into decline under the Japan rulers' policies to weaken the power of temples, but still, there were many sake brewers who would inherit the brewing method of Bodaisen from Nara temples.