Kadyysky District (Russian: Кады́йский райо́н) is an administrative and municipal district (raion), one of the twenty-four in Kostroma Oblast, Russia. It is located in the south of the oblast. The area of the district is 2,190 square kilometers (850 sq mi). Its administrative center is the urban locality (a settlement) of Kadyy. Population: 8,374 (2010 Census); 10,341 (2002 Census); 12,847 (1989 Census). The population of Kadyy accounts for 43.0% of the district's total population.