ISO 3166

ISO 3166 is an international standard that defines codes for the names of countries, dependent territories, and their principal subdivisions. It is published and maintained by the International Organization for Standardization (ISO).

The standard provides short alphabetic and numeric identifiers that are widely used in administration, commerce, logistics, data processing, and technical systems.

Structure

ISO 3166 is divided into three parts:

ISO 3166-1

Defines codes for countries and territories.

It includes three sets of codes:

• Alpha-2 — two-letter codes (e.g., NL, DE, FR)
• Alpha-3 — three-letter codes (e.g., NLD, DEU, FRA)
• Numeric — three-digit numeric codes (e.g., 528, 276, 250)

Alpha-2 codes are commonly used for internet country code top-level domains and various technical standards.

ISO 3166-2

Defines codes for principal subdivisions within countries, such as:

• provinces
• states
• regions
• municipalities (in certain cases)

Subdivision codes are formed by combining the ISO 3166-1 alpha-2 country code with a subdivision identifier.

Example format:

NL-ZH
DE-BY
FR-IDF

ISO 3166-3

Defines codes for former country names that have been removed or replaced in ISO 3166-1. These are used for historical reference and archival consistency.

Purpose

ISO 3166 provides standardized identifiers to ensure consistent country references across:

• international trade
• transportation and logistics
• statistical reporting
• financial systems
• software and database design
• telecommunications and internet infrastructure

The use of standardized codes reduces ambiguity in multilingual and cross-border contexts.

Maintenance

The ISO 3166 Maintenance Agency is responsible for updating and revising the standard. Changes may occur due to:

• state formation or dissolution
• name changes
• territorial restructuring
• administrative reclassification

Updates are published through official ISO channels.

Usage in structured systems

ISO 3166 codes are commonly embedded in technical documentation, metadata fields, domain registration systems, and standardized forms. In such contexts, the codes function as neutral identifiers and do not imply political recognition beyond the scope of the standard itself.

See also

• Country code top-level domains
• Domain Name System
• Country code
• Technical documentation