Stephen Toulouse, known as StepTo to many Xbox gamers, will leave his position as Xbox LIVE policy and enforcement director on February 15.
Toulouse has been with Microsoft for 18 years, but will now explore other opportunities.
"Over the past year I've been doing quite of bit of thinking," wrote Toulouse on his blog. "I turn 40 this year. Despite the wonderful ability in Microsoft to change careers pretty dramatically inside the company, I've been there nearly 18 years and it's the only world I've really ever known. I feel too strangely comfortable, and too strangely tied.
"So over the past several weeks I've made the decision to resign and have been working with my management for an orderly transition. I have no other plans beyond that. I'm a free agent."
He added: "I want to make sure I am clear: This is a positive thing. I have nothing but confidence in the future of Microsoft and specifically Xbox and Xbox LIVE. I have enormous gratitude for my time there. I want to finish my next book, and explore other opportunities."
Microsoft hasn't commented on who, if anyone, will replace Toulouse.