Administrative divisions:

15 regions (wilayas, singular - wilaya); Adrar, Assaba, Brakna, Dakhlet Nouadhibou, Gorgol, Guidimaka, Hodh ech Chargui, Hodh El Gharbi, Inchiri, Nouakchott Nord, Nouakchott Ouest, Nouakchott Sud, Tagant, Tiris Zemmour, Trarza

Definition:

This entry gives the numbers, designatory terms, and first-order administrative divisions as approved by the US Board on Geographic Names (BGN). Changes that have been reported but not yet acted on by the BGN are noted. Geographic names conform to spellings approved by the BGN with the exception of the omission of diacritical marks and special characters.

Source: CIA World Factbook