Netscape Navigator was a proprietary web browser, and the original browser of the Netscape line, from versions 1 to 4.08, and 9.x. It was the flagship product of the Netscape Communications Corp and was the dominant web browser in terms of usage share in the 1990s, but by around 2003 its user base had all but disappeared. This was partly because the Netscape Corporation (later purchased by AOL) did not sustain Netscape Navigator's technical innovation in the late 1990s.

The business demise of Netscape was a central premise of Microsoft's antitrust trial, wherein the Court ruled that Microsoft's bundling of Internet Explorer with the Windows operating system was a monopolistic and illegal business practice. The decision came too late for Netscape, however, as Internet Explorer had by then become the dominant web browser in Windows.

The Netscape Navigator web browser was succeeded by the Netscape Communicator suite in 1997. Netscape Communicator's 4.x source code was the base for the Netscape-developed Mozilla Application Suite, which was later renamed SeaMonkey. Netscape's Mozilla Suite also served as the base for a browser-only spinoff called Mozilla Firefox.

The Netscape Navigator name returned in 2007 when AOL announced version 9 of the Netscape series of browsers, Netscape Navigator 9. On 28 December 2007, AOL canceled its development but continued supporting the web browser with security updates until 1 March 2008. AOL allows downloading of archived versions of the Netscape Navigator web browser family.