Karahisar (former Karaasar) is a town in Tavas district of Denizli Province, Turkey. It is situated at 37°37′N28°57′E / 37.617°N 28.950°E / 37.617; 28.950 along the Akçay creek, a tributary of Büyükmenderes River (historical Maeander). The distance to Tavas is 10 kilometres (6.2 mi). The population of Karahisar is 3656  as of 2011. The settlement was founded in 1530s by Turkmens. The earlier name of the settlement Karaasar probably refers to Kara Fatma, the wife of the tribe. Gülfem one of the concubines of Suleyman I, the Ottoman sultan (also called the Magnificent) commissioned a mosque and a fountain in the settlement. In 1954 the settlement was declared a seat of township.