Ghardaïa (gärdäyäˈ) [key], town (1998 pop. 110,724), N Algeria. It is the chief town of the Mzab, a stony, barren valley of the N Sahara. Ghardaïa is a center of date production and of the manufacture of rugs and cloth. The city was founded in the 11th cent. by Muslim Kharijite sectaries fleeing persecution by the orthodox Muslims of the north. First occupied by French troops in 1854, Ghardaïa was not officially annexed to France until 1882.