It defines three sets of country codes: ISO 3166-1 alpha-2 – two-letter country codes which are the most widely used of the three, [citation needed] and used most prominently for the Internet's country code top-level domains (with a few exceptions). The two-letter country abbreviation for Vietnam is VN, the three-letter code is VNM International Telephone Code of Vietnam 84 The Vietnam telephone country code is the number 84. 1. About Vietnam country code A country code, also known as an international subscriber dialing (ISD) code, is a telephone number prefix utilized in international direct dialing (IDD) to route calls to a country different from the caller's. The country code is in use for example for the two-letter suffixes such as .us (United States), .fr (France) or .de (Germany) in top-level domains (for countries) on the Internet. l11zD.