Kosonsoy (also spelled Kasansay or Kasan) is a city located in the Namangan Region of Uzbekistan. It serves as the administrative seat of the Kasansay District.
The city derives its name from the local geography, specifically the River Kasan. This river flows from the high mountains of Kyrgyzstan into the Turakurgan District. The suffix "soy" is a Sugdian-Tajik word meaning "brook," reflecting the area's hydrological characteristics.