As a national of Mauritania, you are required to have a Vietnam visa prior to your trip to Vietnam.
We are sorry that your nationality has not been supported with Vietnam visa on arrival which is applied online. You are advised to contact the nearest or most convenient Vietnam Embassy or the Vietnam Immigration Department to apply for visa to Vietnam.

For Vietnam Immigration Department contact
Vietnam Immigration Department (A18)
Add 44- 46 Tran Phu Street, Ba Dinh District, Hanoi, Vietnam
Tel: +84 4 38257941 Fax: 04 38243287 / 88