The Sous or Souss (Berber: Tamazirt n Sus, Arabic بلاد السوس bilād as-Sūs) is a region in southern Morocco. Geologically, it is the alluvial basin of the Oued Sous (Asif n Sus), separated from the Sahara by the Anti-Atlas Mountains. The natural vegetation in the Sous is savanna dominated by the Argan (Argania spinosa), a local endemic tree found nowhere else; part of the area is now a UNESCO Biosphere Reserve to protect this unique habitat. A well irrigated area, this has been one of Morocco’s most fertile regions for centuries, known since at least the eleventh century for its cultivation and export of sugar. The golden age of the Sous was in the seventeenth century during the era of the kingdom of Tazerwalt, when the region enjoyed autonomy and profited from both the trans-Saharan gold trade and the sale of sugar to Portuguese, Dutch and English traders. The centre for foreign trade during this time was Agadir, a city 10 km north of the mouth of the Sous river. The Sous is inhabited by Berber peoples; aside from some Arabic-speaking tribes, the main inhabitants are the Chleuh (ašlḥi, Shilha, Sousis), speakers of a distinct Berber language called Shilha or Sous Berber (Tashelhiyt or Tasoussit).