Mozilla is a free software community founded in 1998 by members of Netscape. The Mozilla community uses, develops, publishes, and supports Mozilla products, thereby promoting free software and open standards. The community is supported institutionally by the non-profit Mozilla Foundation and its tax-paying subsidiary, the Mozilla Corporation.

Mozilla's current products include the Firefox web browser, Thunderbird e-mail client (now through a subsidiary), the Bugzilla bug tracking system, and the Gecko layout engine.

On January 23, 1998, Netscape announced that its Netscape Communicator browser software would be free, and that its source code would also be free. One day later, Jamie Zawinski of Netscape registered mozilla.org. The project took its name, "Mozilla", from the original code name of the Netscape Navigator browser—a portmanteau of "Mosaic and Godzilla", and used to coordinate the development of the Mozilla Application Suite, the free software version of Netscape's internet software, Netscape Communicator. Zawinski said he arrived at the name "Mozilla" at a Netscape staff meeting. A small group of Netscape employees were tasked with coordinating the new community.

Mozilla originally aimed to be a technology provider for companies such as Netscape, who would commercialise their free software code. When Netscape's parent company AOL greatly reduced its involvement with Mozilla in July 2003, the Mozilla Foundation was designated the project's legal steward. Soon after, Mozilla deprecated the Mozilla Suite in favor of creating independent applications for each function, primarily the Firefox web browser and the Thunderbird email client, and moved to supply them directly to the public.

Mozilla's activities next expanded, and also experienced product terminations, with Firefox on mobile platforms (primarily Android), a mobile OS called Firefox OS (since cancelled), a web-based identity system called Mozilla Persona (since cancelled) and a marketplace for HTML5 applications.

In a report released in November 2012, Mozilla reported that its revenue for 2011 was $163 million, up 33% from $123 million in 2010. It noted that roughly 85% of their revenue came from their contract with Google.

At the end of 2013, Mozilla announced a deal with Cisco, whereby Firefox would download and use a Cisco-provided binary build of an open-source codec to play the proprietary H.264 video format. As part of the deal, Cisco would pay any patent licensing fees associated with the binaries that it distributed. Mozilla's CTO, Brendan Eich, acknowledged that it was "not a complete solution" and wasn't "perfect". An employee in Mozilla's video formats team, writing unofficially, justified it by the need to maintain their large user base, which would be necessary for future battles for truly free video formats.

In December 2013, Mozilla announced funding for the development of paid games through its Game Creator Challenge. However, even games that would be released under non-free or free software licenses were required to be made with open web technologies and Javascript. In January 2017 the company rebranded away from its dinosaur symbol in favor of a logo including a "://" character sequence from a URL: "moz://a". As a part of the rebranding, it commissioned the open source slab serif font Zilla Slab.