Some village communities of the mountain-dwelling, Tibeto-Burman speaking Lahu peoples support temples and an associated priesthood, whose principal purpose is to honour their creator-divinity G'ui sha. Neither temples nor ritual devotion to a High God are commonly present among the Lahu people's upland neighbours. Relatively small spirit shrines are the principal form of ritual architecture and high gods are typically seen as being unconcerned with human affairs; consequently, it can serve no useful purpose to “worship” them. This paper seeks to demonstrate that these peculiarities of Lahu custom and belief derive from a Mahayanist movement that swept through the Lahu mountain homelands in southwestern Yunnan, probably beginning in the late seventeenth to mid eighteenth centuries CE. The result was (a) the establishment of temples as the principal form of religious architecture among many (not all) Lahu communities and an identification of their high-god G'ui sha with the Buddha Śākyamuni and consequently–following Mahāyānist ideology – with transcendental Buddhahood.