Ulken Koskopa (Kazakh: Үлкен Қосқопа;[1] Russian: Большая Коскопа)[2] is a salt lake in Nauyrzym District, Kostanay Region, Kazakhstan.

[5] The name Koskopa in the Kazakh language means "Double Kopa" —"Kopa" referring to a lake that seasonally becomes a salt marsh overgrown with reeds and sedges.

Small river Karasu flows in from the north and twin lake Kishi Koskopa is very close to the south, both lakes being joined by a short 250 meters (820 ft) wide sound.

[3] Ulken Koskopa has roughly a kidney shape, stretching for almost 4 kilometers (2.5 mi) in an east–west direction.

[5][7] Typha and Phragmites reeds grow in Ulken Koskopa.