The Open Directory Project (ODP), also known as Dmoz (from directory.mozilla.org, its original domain name), is a multilingual open content directory of World Wide Web links. It is owned by Netscape but it is constructed and maintained by a community of volunteer editors.

ODP uses a hierarchical ontology scheme for organizing site listings. Listings on a similar topic are grouped into categories which can then include smaller categories.

ODP was founded in the United States as Gnuhoo by Rich Skrenta and Bob Truel in 1998 while they were both working as engineers for Sun Microsystems. Chris Tolles, who worked at Sun Microsystems as the head of marketing for network security products, also signed on in 1998 as a co-founder of Gnuhoo along with co-founders Bryn Dole and Jeremy Wenokur. Skrenta had developed TASS, an ancestor of tin, the popular threaded Usenet newsreader for Unix systems. Coincidentally, the original category structure of the Gnuhoo directory was based loosely on the structure of Usenet newsgroups then in existence.

The Gnuhoo directory went live on June 5, 1998. After a Slashdot article suggested that Gnuhoo had nothing in common with the spirit of free software, for which the GNU project was known, Richard Stallman and the Free Software Foundation objected to the use of Gnu. So Gnuhoo was changed to NewHoo. Yahoo! then objected to the use of "Hoo" in the name, prompting them to switch the name again. ZURL was the likely choice. However, before the switch to ZURL, NewHoo was acquired by Netscape Communications Corporation in October 1998 and became the Open Directory Project. Netscape released the ODP data under the Open Directory License. Netscape was acquired by AOL shortly thereafter and ODP was one of the assets included in the acquisition. AOL later merged with Time-Warner.
ODP size by date.

By the time Netscape assumed stewardship, the Open Directory Project had about 100,000 URLs indexed with contributions from about 4500 editors. On October 5, 1999, the number of URLs indexed by ODP reached one million. According to an unofficial estimate, the URLs in the Open Directory numbered 1.6 million in April 2000, surpassing those in the Yahoo! Directory. ODP achieved the milestones of indexing two million URLs on August 14, 2000, three million listings on November 18, 2001 and four million on December 3, 2003.

From January 2006 the Open Directory published online reports to inform the public about the development of the project. The first report covered the year 2005. Monthly reports were issued subsequently until September 2006. These reports gave greater insight into the functioning of the directory than the simplified statistics given on the front page of the directory. The number of listings and categories cited on the front page include "Test" and "Bookmarks" categories but these are not included in the RDF dump offered to users. The total number of editors who have contributed to the directory as of March 31, 2007 was 75,151. There were about 7330 active editors during August 2006.