The domain name org is a generic top-level domain (gTLD) of the Domain Name System (DNS) used in the Internet. The name is derived from organization.

The org domain was one of the original top-level domains, with com, edu, gov, mil and net, established in January 1985. It was originally intended for non-profit organizations or organizations of a non-commercial character that did not meet the requirements for other gTLDs. The MITRE Corporation was the first group to register an org domain with mitre.org in July 1985.

Registrations in the org are processed via accredited registrars worldwide. Anyone can register an org second-level domain. Although org was recommended for non-commercial entities, there are no restrictions to registration. There are many instances of org being used by commercial sites. org was also commonly recommended for use by individuals, although name and info are now alternatives. According to the company's Dashboard (Domain Name) report, the composition of .ORG is diverse, including cultural institutions, associations, sports/teams, religious, civic, open source software (such as  Drupal, Joomla), schools, environmental initiatives, social/fraternal organizations, health, legal services, clubs and community volunteer groups. There are also cases where companies or organizations have created sites under .ORG for crisis management.

The org TLD has been operated since January 1, 2003 by Public Interest Registry, who assumed the task from VeriSign Global Registry Services, a division of VeriSign.

On 17 March 2010 The Public Interest Registry announced that there are over 8 million domain names registered as .org, making it the third largest generic top-level domain (gTLD).