20 Ouguiya

Mauritania's ouguiya is one of only two world currencies not based on a decimal system — one ouguiya divides into five khoums, a structure rooted in traditional West African exchange ratios rather than colonial monetary convention. France had issued the CFA franc across the region, but Mauritania abandoned it in 1973 upon establishing the Banque Centrale de Mauritanie and introducing its own currency as a deliberate assertion of post-independence economic policy.

The bimetallic format arrived with the 2009 series, replacing an earlier monometallic issue of the same denomination.