The Sviyaga (Russian: Свияга, Tatar Cyrillic: Зөя, Latin: Zöyä, Chuvash: Сĕве) is a river in the Ulyanovsk Oblast and Tatarstan, a right tributary of the Volga River. It has a length of 375 km. The area of the basin is 16,700 km². The Sviyaga River flows into the Sviyaga Cove of the Kuybyshev Reservoir, west of Kazan. It freezes up in November-December and stays under the ice until April-May. Major tributaries are Arya, Bula, Karla, Kubnya, and Tosha rivers.
The city of Ulyanovsk is located on the Sviyaga River. In Ulyanovsk, Sviyaga flows only a few miles away from the Volga, but their confluence is about 200 km north from Ulyanovsk.
The castle of Sviyazhsk dates back to 1551 is situated at the island in Sviyaga Cove of the Kuybyshev Reservoir.
Coordinates: 55°43′52″N 48°36′57″E / 55.73111°N 48.61583°E