Acıgöl (literally "the bitter lake" in Turkish) is a lake in Turkey's inner Aegean Region, in an endorheic basin at the junction between Denizli Province, Afyonkarahisar Province and Burdur Province. Its surface area varies greatly through the seasons, with 100 km² in spring and 35 km² in late summer, with a maximum depth of 1.63 m. The lake is notable for its sodium sulfate reserves extensively used in the industry and Turkey's largest commercial sodium sulfate production operations are based here. It is situated 60 km east of Denizli city.