Ostashkovsky District is an administrative and municipal district (raion), one of the thirty-six in Tver Oblast, Russia. It is located in the northwest of the oblast and borders with Demyansky District of Novgorod Oblast in the north, Firovsky District in the northwest, Kuvshinovsky District in the east, Selizharovsky District in the south, Penovsky District in the southwest, and with Maryovsky District of Novgorod Oblast in the west. The area of the district is 3,200 square kilometers (1,200 sq mi). Its administrative center is the town of Ostashkov. Population: 23,761 ; 7,357 (2002 Census); 8,921 (1989 Soviet census). The population of Ostashkov accounts for 76.1% of the district's total population.

Demyansky District is an administrative and municipal district (raion), one of the twenty-one in Novgorod Oblast, Russia. It is located in the south of the oblast and borders with Krestetsky District in the north, Valdaysky District in the northeast, Firovsky District of Tver Oblast in the southeast, Ostashkovsky District of Tver Oblast in the south, Maryovsky District in the southwest, Starorussky District in the west, and with Parfinsky District in the northwest. The area of the district is 3,200 square kilometers (1,200 sq mi). Its administrative center is the urban locality of Demyansk. Population: 13,001 (2010 Russian census); 16,020 ; 18,488 (1989 Soviet census). The population of Demyansk accounts for 41.3% of the district's total population.