Steven Sinofsky, the head of Microsoft’s Windows division, has left the company with immediate effect.
His departure comes just weeks after Microsoft launched Windows 8, the latest edition of its flagship product, seen as key to the firm’s future.
Microsoft did not give any reason for Mr Sinofsky’s departure.
However, industry watchers suggest that the real reason could be an internal “war” between him and chief executive Steve Ballmer.
Markets took the news badly, with Microsoft’s shares losing 4% in Tuesday morning trading on Wall Street.
The company said Julie Larson-Green would be promoted to lead all Windows software and hardware engineering.
“This is shocking news. This is very surprising,” said Brendan Barnicle, an analyst at Pacific Crest Securities.
He added that many observers saw Mr Sinofsky as a potential successor to Steve Ballmer, Microsoft’s chief executive.
Source: BBC News