Mauritania, formally the Islamic Republic of Mauritania, is a sovereign country in Northwest Africa. It is bordered by the Atlantic Ocean to the west, Western Sahara to the north and northwest, Algeria to the northeast, Mali to the east and southeast, and Senegal to the southwest. By land area Mauritania is the 11th-largest country in Africa and 28th-largest in the world; 90% of its territory is in the Sahara.