ay river (, ) is a river in bashkortostan and chelyabinsk oblast in russia, a left tributary of the ufa river. the river is long, and its drainage basin covers . the ay freezes up in late october or early november and remains icebound until mid-april. the cities of zlatoust and kusa are along the ay river. along the banks of the river, there are many steep cliff sides and caves. the current of the river has been used for hydroelectric power. it is also possible to fish for pike, bleak, and carp, to name a few species.