Microsoft says it has signed a deal to buy the professional social networking site LinkedIn for $26.2bn.
LinkedIn's shares surged 48 percent to $194.28 on Monday, in a deal that the chairman of LinkedIn's board, Reid Hoffman, defined as a "re-founding moment".
According to a statement from the two companies, LinkedIn "will retain its distinct brand, culture and independence".
LinkedIn CEO Jeff Weiner will remain CEO of the social networking site but will report directly to Microsoft CEO Satya Nadella.
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"Just as we have changed the way the world connects to opportunity, this relationship with Microsoft, and the combination of their cloud and LinkedIn's network, now gives us a chance to also change the way the world works," Weiner said in a statement.
Microsoft said it would pay $196 per share for the company and would issue new debt to fund the deal.
The deal, Microsoft's biggest ever, is expected to be completed later this year.
The move comes as the Seattle-based company refocuses its efforts from being a pure software firm, and LinkedIn seeks ways to boost growth.
LinkedIn, which enables members to connect with similar-minded professionals and facilitates job hunting, has some 433 million members worldwide.