A domain name registry, is a database of all domain names registered in a top-level domain. A registry operator, also called a Network Information Center (NIC), is the part of the Domain Name System (DNS) of the Internet that keeps the database of domain names, and generates the zone files which convert domain names to IP addresses. Each NIC is an organisation that manages the registration of Domain names within the top-level domains for which it is responsible, controls the policies of domain name allocation, and technically operates its top-level domain. It is potentially distinct from a domain name registrar.

Domain names are managed under a hierarchy headed by the Internet Assigned Numbers Authority (IANA), which manages the top of the DNS tree by administrating the data in the root nameservers.

IANA also operates the .int registry for intergovernmental organisations, the .arpa zone for protocol administration purposes, and other critical zones such as root-servers.net.

IANA delegates all other domain name authority to other domain name registries such as VeriSign.

Country code top-level domains (ccTLD) are delegated by IANA to national registries such as DENIC in Germany, or Nominet in the United Kingdom.