Finnish mobile phone giant Nokia is paying 264m euros ($410m; £209m) to buy out the other shareholders in handset software firm Symbian.
Nokia, which already owns 48% of the UK-based firm, intends to develop its software to compete with Google's planned Android operating system.
Nokia said Sony Ericsson, Ericsson, Panasonic and Siemens had agreed to sell their stakes in Symbian.
It added that Samsung was also expected to accept the offer.
For its part, Symbian said the takeover was "a fundamental step" in the establishment of the Symbian Foundation, which is expected to start operating in the first half of 2009.
The foundation will bring together Nokia, AT&T, LG, Motorola, NTT Docomo, Samsung, Sony Ericsson, STMicroelectronics, Texas Instruments and Vodafone in collaboration on a new, royalty-free open software platform for mobile phones.
According to Nigel Clifford, chief executive of Symbian, it could signal a sea-change in how the software platform is developed.
"We're freeing up innovation - this is epoch-making. Nothing like this has been put into the open-source community before."
The aim is to unite several different existing operating systems - Symbian OS, S60, UIQ and MOAP.
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