Country calling codes

Calling distinguishes official country-related code systems: ITU-T E.164 telephone country codes, IANA root-zone / ccTLD delegations, and UN M49 statistical area codes—linked to issuers so the systems are not treated as interchangeable.

Item	Issuer or maker	Detail	Source
ITU-T E.164 assigned country codes	International Telecommunication Union (ITU)	The ITU publishes the List of Recommendation ITU-T E.164 assigned country codes as an official reference for international telephone numbering assignments.	www.itu.int
IANA Root Zone Database	Internet Assigned Numbers Authority (IANA)	The IANA Root Zone Database lists delegation details for top-level domains, including generic top-level domains and country-code top-level domains.	www.iana.org
UN M49 Standard country or area codes	United Nations Statistics Division (UNSD)	The United Nations Statistics Division publishes the M49 Standard country or area codes for statistical use, providing standardized geographic identifiers and classifications.	unstats.un.org
ISO 3166-1 alpha-2 country codes	International Organization for Standardization (ISO)	ISO 3166-1 alpha-2 two-letter codes underpin many ccTLD labels and are distinct from E.164 numeric dialing codes.	www.iso.org
ISO 3166-1 alpha-3 codes	ISO 3166 Maintenance Agency	Three-letter alpha-3 codes provide another ISO country identifier used in statistics and travel documents.
ISO 3166-1 numeric codes	ISO country coding numeric track	Numeric 3166-1 codes align closely with UN M49 identifiers but remain an ISO maintenance product.
ICANN ccTLD oversight context	Internet Corporation for Assigned Names and Numbers	ICANN coordinates global DNS policy while IANA publishes the authoritative root-zone delegation database.	www.icann.org
IETF E.164 mapping RFCs	Internet Engineering Task Force	IETF documents discuss ENUM and other mappings between E.164 numbers and Internet identifiers without merging code systems.	www.ietf.org
GSMA numbering resources	GSM Association	GSMA publishes mobile numbering and roaming references that depend on national E.164 assignments.	www.gsma.com
NANPA North American Numbering Plan	North American Numbering Plan Administration	NANPA administers the shared country code +1 numbering resources for the North American Numbering Plan.	www.nationalnanpa.com
ITU-T E.123 presentation guidance	ITU Telecommunication Standardization Sector	E.123 gives notation guidance for national and international telephone numbers distinct from assigning country codes.