The Zay (; ) is a river in Russia, a left-bank tributary of the Kama. It is long, and its drainage basin covers . It begins near Mikhaylovka, Leninogorsky District, Tatarstan and falls to the Kama south-west of Nizhnekamsk.
At its headwaters the river is named the Steppe Zay (, Stepnoy Zay, , Dala Zäye). The lower reach of the river after the confluence with Forest Zay River, , is named simply Zay. One of headstream Steppe Zay's tributaries is also named Zay. Other major tributaries are the Moshkara, Zay-Karatay, Ursala, Aktashka, and Shumyshka rivers.
The mineralization varies from 2000âÂÂ3000 to 5000âÂÂ8000 mg/L. Average sediment deposition at the river mouth per year is . Drainage is regulated. There are two reservoirs, Zainsk and Karabash Reservoirs constructed in Zay valley. Since 1978 it is protected as a natural monument of Tatarstan. Zainsk, Almetyevsk and Karabash are located on the river.