Kalyazinsky District (Russian: Каля́зинский райо́н) is an administrative and municipal district (raion), one of the thirty-six in Tver Oblast, Russia. It is located in the southeast of the oblast and borders with Uglichsky District of Yaroslavl Oblast in the northeast, Pereslavsky District of Yaroslavl Oblast in the southeast, Sergiyevo-Posadsky District of Moscow Oblast in the south, Taldomsky District, also of Moscow Oblast, in the southwest, Kimrsky District in the west, and with Kashinsky District in the northwest. The area of the district is 1,671 square kilometers (645 sq mi). Its administrative center is the town of Kalyazin. Population: 21,688 (2010 Census); 24,460 (2002 Census); 27,341 (1989 Census). The population of Kalyazin accounts for 63.9% of the district's total population