November 2, 2004: Firefox Comes to the Mac
When OS X first debuted, the browser of choice was Internet Explorer 5. Then Apple released Safari, a direct competitor to Internet Explorer.
Microsoft used the introduction of Safari as the reason the company stopped development of IE for the Mac, but the consensus was that Safari was developed precisely because Microsoft was planning on dumping IE for the Mac. In any event, Mac users were suddenly left with exactly one mainstream up-to-date browser.
That changed when the wildly popular, market share grabbing, open source browser Firefox was released for the Mac this month in 2004.

Comments
I knew there was something wrong with this article as I read it. According to an article about FireFox on Wikipedia, there was a Mac version of FireFox as far back as 2003.
I should have been clearer, it was the release of Firefox 1.0, the previous versions were available but they were “technology previews” not final releases.