Sviyazhsk or Zöyä (Russian: Свия́жск; Tatar Cyrillic: Зөя, Latin: Zöyä) is a rural locality (a selo) in the Republic of Tatarstan, Russia, located at the confluence of the Volga and Sviyaga Rivers. It is situated on an island since the construction of the Kuybyshev Reservoir at Tolyatti downstream Volga in 1955.
Sviyazhsk was founded in 1551 as a fortress, which was built within four weeks from parts made in Uglich and transported down the Volga. It became a military base of the Russian army during the siege of Kazan (1552).
Since the 15th century, Sviyazhsk served as a center of an uyezd. In 1920–1927, it was a center of Sviyazhsky Kanton; in 1927–1931—the administrative center of Sviyazhsky District. In 1932, it was demoted to rural status.
There is a school and a club in Sviyazhsk, as well as a monastery associated with the name of Macarius of Unzha.
Sviyazhsk railway station is located 6 kilometers (3.7 mi) west of the island and is linked with Sviyazhsk proper by a highway running along the dike.