Trarza is a region in southwest Mauritania. Its capital is Rosso. Other major cities and towns include Mederdra and Boutilimit. Trarza borders the regions of Inchiri and Adrar to the north, Brakna to the east, and the country of Senegal to the south. Its western coastline on the Atlantic Ocean is interrupted only by the Mauritanian capital Nouakchott, which the region completely surrounds.