.org (organization) is a generic top-level domain (gTLD) used in the Internet's Domain Name System. No pronunciation, whether "dot org" or "dot O-R-G", has been established.

.org was one of the original top-level domains, established in January 1985, originally intended for use by organizations that did not meet the requirements for other gTLDs. Now anyone can register a .org domain. .org was the domain commonly recommended for use by individuals, although .name and .info are now alternatives.

The .org TLD has been operated since 1 January 2003 by Public Interest Registry.

Although organizations anywhere in the world can register .org domains, many countries have a second-level domain with a similar purpose under their own country code TLD. Such second-level domains are usually of the form .org.xx or .or.xx, where xx is the ccTLD.

The .org TLD is sometimes associated with the open source/free software movement, as opposed to the .com domains used mostly by companies. While it is true that many open source projects use .org domains (OpenOffice.org even has it in the product name), most .org domains do not qualify for this generalization.