
Previously vice-president of Xbox Europe, Gosen has left his job 'to explore new opportunities'. It is not known if he has a job to go to.
Gosen joined Microsoft, Xbox's parent company, in 2008, having previously been head of marketing at Nintendo. He has overseen marketing for the Xbox 360 and the growth of Xbox's online community Live.
Lewis will now take over marketing responsibilities for Xbox. The console is preparing to launch Project Natal, technology that enables gamers to control characters in games through a motion-sensor rather then the traditional games controller.
Project Natal is expected to launch in the UK before Christmas.