The website will feature various ads plugging the launch of Mario vs Donkey Kong and Super Mario Ball, both of which are released this month.
Two of Nintendo’s existing games, Mario Golf: Advance Tour and Paper Mario: The Thousand Year Door, which are being launched for the Nintendo Gamecube, will also be promoted on the site.
Users of the site will also be able to play Mario games and download related wallpapers and screensavers.
A television campaign will accompany the online activity during the five-week deal, directing CITV viewers to the site.
Rob Lowe, UK product manager at Nintendo UK, said: "Mario Month is an excellent way of promoting five great Mario games this November, and the deal between CiTV and Nintendo is a superb way to encapsulate the Mario look and feel both on-line, and on television."
Jeremy Rosenberg, online sales manager at ITV Sales, added: “The Mario Month is a ground breaking campaign for CiTV as it is the first time ITV has incorporated an integrated ad to be shown within broadcast to drive kids to www.itv.com/citv.”