Nokia has decided to adopt Microsoft's Windows Phone 7 as its chief platform.
This means Symbian will no longer be the main OS running on Nokia devices.
Symbian will now become a "franchise platform" and Nokia believes it will sell another 150 million Symbian devices in the coming years.
Steve Ballmer, chief executive (CEO) of Microsoft, revealed the partnership had already started work on developing a Windows-based Nokia device.
There was no confirmation of what that device would be or when it would hit the shelves.
Stephen Elop, CEO of Nokia, said the pair will unite to create some groundbreaking mobile technology.
"We have the opportunity to disrupt the trajectory in the battle of the ecosystems," Elop said.
"We also think this is good for Microsoft, they too can play a leading role in creating a new ecosystem."
As for MeeGo, Nokia still plans to push out a phone based on the operating system before the end of 2011.
However, MeeGo has now become an open source OS project and more of an experiment to learn about what the future holds for mobile software, Elop said.
"We'll try and anticipate what the next change is in the mobile ecosystem."
Further reorganisation
It will come as no surprise that Elop has made some more changes at the top of Nokia, after his memo warning the company was atop a "burning platform."
Alberto Torres has stepped down from the management team in his role as vice president for MeeGo Computers.
Elsewhere, Elop has organised the company into two distinct units: Smart Devices and Mobile Phones.
Jo Harlow, currently senior vice president for marketing at Nokia Mobile Phones, will head the Smart Devices division and will be responsible for creating the Nokia Windows Phone portfolio.
Mary McDowell, currently executive vice president in charge of Nokia's Mobile Phones unit, will head up the mobile segment, with which Nokia will hope to help connect people in developing countries.
Talking about the company reshuffle, Elop admitted there will be "substantial reductions in employment" across the world.
"We do not have numbers, but we are working very hard to understand that," the Elop said.
Despite the fact Elop, McDowell and Harlow all come from outside of Finland, the CEO stressed the importance of the country to Nokia's future.
There have been rumours of Nokia drastically reducing operations in Finland and upping activity in the US.
"Let me make a really important statement Nokia is first and foremost a Finnish company," he added.
"Finland is our home and it will remain our home. More than anything else, make Nokia a success for Finland."
The announcements come after a turbulent few months for the Finnish manufacturer, which culminated in the leak of an Elop memo warning the company was standing on a "burning platform."
"We have been on a complex journey but we are traveling on a path forward," Elop added.
