Rosso is the major city of south-western Mauritania and capital of Trarza region. It is situated on the Senegal River at the head of year-round navigation. The town is 204 km south of the capital Nouakchott. The Arabic name is Al-Quwarib. Rosso was once the capital of the Emirate of Trarza, a Precolonial Sahrawi dominated state. Under French colonial rule Senegal and Mauritania were administered as a single entity. When independence came, the new frontier was drawn along the Senegal River, thus splitting the small town of Rosso in two. This article refers to Mauritanian Rosso, on the northern bank of the river.
Originally a staging-post for the gum arabic trade, Rosso has grown rapidly since independence. From a population of a mere 2 300 in 1960 it has now overtaken Kaédi to become the 3rd largest city in the country with 48 922 inhabitants (2000 census).