This wiki page lists Ubuntu 4.10 (Warty Warthog) as the first Ubuntu released by Canonical Ltd.
But I wanted to know whether there ever was an Ubuntu 1.x, as in Windows or Mac OS. If yes, is it available somewhere?
Ubuntu's version numbers are made using the year and month of their release date: Ubuntu 12.04 was released in April 2012, Ubuntu 11.10 on October 2011 and so on.
Ubuntu 4.10 was released in October 2004 and is the first Ubuntu release. As there wasn't any Ubuntu version released in 2001 there is no Ubuntu 1.x.