Steven Sinofsky, the head of Microsoft's Windows division and the executive widely expected to be the next CEO, has left the company with immediate effect.
No official reason was given for Steven Sinofsky's departure from Microsoft after 23 years and less than three weeks after the official launch of Windows 8 and the first Microsoft-branded computer.
Neither Microsoft CEO Steve Ballmer nor Sinofsky gave an explanation, although US reports cited an unnamed senior executive at the company as saying the decision was "mutual".
The changes in leadership were aimed at ensuring Microsoft continued to be a dominant player in the sector, Ballmer said in a statement.
Sinofsky did not announce any future plans, but said in a statement: "It is impossible to count the blessings I have received over my years at Microsoft. I am humbled by the professionalism and generosity of everyone I have had the good fortune to work with at this awesome company."
Microsoft said Julie Larson-Green would be promoted to lead all Windows software and hardware engineering.
Sinofksy's departure is the latest shock departure in the technology sector, coming a month after Apple announced the departure of Scott Forstall, head of its iOS software, and John Browett, head of retail.
"The pace at which changes are happening in the industry is so intense that companies are struggling to keep up with it," Manoj Menon of consulting firm Frost & Sullivan told the BBC.
The changes in leadership, he said, are a reflection of the fact that business models are changing, that competition is coming from unexpected quarters and that economic challenges are getting tougher.