​TIBESTI, a mountainous and little known region of the central Sahara, inhabited by the Tibbu (q.v.). The country was partly explored in 1870 by Gustav Nachtigal; it had not been again visited by Europeans up to 1910, though French officers had reached Borku on its southern borders. By the Anglo-French declaration of the 21st of March 1899 Tibesti was included in the French sphere of influence in North Africa.