Kadyy is an urban-type settlement located in Russia. It serves as the administrative center of the Kadyysky District within the Kostroma Oblast.
According to census data, the population of Kadyy has seen a gradual decline over several decades. The 2021 census recorded a population of 3,102 residents, following figures of 3,597 in 2010, 3,882 in 2002, and 4,147 during the 1989 Soviet census.