Ephemeral wetland vegetation of the Ob River is defined within the limits of Novosibirsk Region and Altai Territory, Russia. Association Cypero fusci-Limoselletum aquaticae (Oberd. 1957) Korneck 1960 (Eleocharition soloniensis Philippi 1968, Nanocyperetalia Klika 1935, Isoëto-Nanojuncetea) prevails on the Ob River low water banks in the forest-steppe zone. The association is represented by regional variant Riccia frostii. Communities of Peplido alternifoliae-Alismatetum graminei ass. nov. (Nanocyperion Koch 1926, Nanocyperetalia) develop on dirty roads of riparian zone high levels in years of high floods. The new association diagnostic species are Lindernia procumbens and Scirpus supinus. Subassociation Cypero-Limoselletum scirpetosum lateriflori Taran 1995 is transferred to the Peplido alternifoliae-Alismatetum graminei association as variant Cyperus fuscus. The author’s data defining ephemeral wetland vegetation of the forest-steppe zone of Western Siberia (73 relevés), including subassociation Eleocharito-Caricetum bohemicae gnaphalietosum rossici Taran 1995 dominating on the low water banks of the Biya River lower course, are summed up in the synoptic table.