Ayun Hạ Reservoir or Ayun Hạ Lake (Vietnamese: Hồ Ayun Hạ) is an artificial lake in Gia Lai Province, Vietnam. The lake was formed when the Ayun River was stopped early in 1994, to start the construction of a dam and lake for irrigation. The flooded area of the lake district belongs to the commune of HBong Chu Se.

The lake has a surface area of 37 km (14 sq mi), and has a length of 25 km (16 mi), and is 5 km (3.1 mi) at its widest.