Calling Mauritania from the United States explained:

• 011 - US exit code; dial first for international calls made from the USA or Canada
• 222 - Country Code for Mauritania
• Phone Number - 8 digits, landlines can start with 25, 35 and 45 (example: 25?? ????); all other numbers are cellular phones
• US to Mauritania international dialing format: 011 222 ???? ????

Phone Books:

• Yellow Pages of Africa

Updates:

• Mauritania telephone numbering changes - January 2011