Trarza (Arabic: ولاية الترارزة) is a region in southwest Mauritania. Its capital is Rosso. Other major cities and towns include Mederdra and Boutilimit. The region borders the Mauritanian regions of Inchiri and Adrar to the north, Brakna to the east and Senegal to the south (to the west is the Atlantic Ocean). The Mauritanian capital, Nouakchott, and the capital district are geographically part of the region.