On a base of Braun-Blanquet vegetation classification, natural poplar (Populus laurifolia, Populus nigra) forests of the Charysh, Biya and Katun Rivers are defined. The forests are located in areas where the rivers exit from Altai mountains on Praealtai plain. The middle Charysh poplar forests form association Populetum laurifolio-nigrae Taran (1997)2015, the lower Biya ones – ass. Viburno opuli-Populetum laurifoliae Taran 1997, the lower Katun ones – subass. Equiseto hyemalis-Populetum nigrae violetosum irinae Taran 1997. The forests species composition, phytocoenotic sructure and habitat conditions are detailed defined. The review of the literature about forests dominated Populus laurifolia is given. Poplar (Populus laurifolia, P. nigra) forests of the Ob River mountain tributaries form alliance Populion laurifolio-nigrae Taran 2015 (Salicetalia purpureae Moor 1958, Salicetea purpureae Moor 1958). The alliance areal envelopes mountain and piedmont reaches of river floodplains located on the north and west macroslopes of the Altai Mountains and also the Tom River upper course.