|Zay, Steppe Zay River|
|Origin||Mikhaylovka, Leninogorsky District, Tatarstan, Russia|
|Mouth||Kama River,near Nizhnekamsk, Tatarstan, Russia|
|Basin countries||Tatarstan, Russia|
|Length||270 km (170 mi)|
|Mouth elevation||53 m (174 ft)|
|Avg. discharge||489 m3/s (17,300 cu ft/s), maximum in 1979 near Staroye Palchikovo|
|Basin area||5,020 km2 (1,940 sq mi)|
The Zay (Russian: Зай; Tatar: Cyrillic Зәй, Latin Zäy, pronounced [zæɪ]) is a river in Tatarstan, Russian Federation, a left-bank tributary of the Kama River. It is 270 kilometres (170 mi) long, and its drainage basin covers 5,020 square kilometres (1,940 sq mi). It begins near Mikhaylovka, Leninogorsky District, Tatarstan and falls to the Kama River 7 kilometres (4 mi) south-west of Nizhnekamsk.
At its headwaters the river is named the Steppe Zay (Russian: Степной Зай, Stepnoy Zay, Tatar: Cyrillic Дала Зәе, Latin Dala Zäye). The lower reach of the river after the confluence with Forest Zay River, 55 kilometres (34 mi), is named simply Zay. Also, 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 2000-3000 to 5000–8000 mg/l. Average sediment deposition at the river mouth per year is 130 millimetres (5.1 in). 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, Tatarstan are along the river.