'The South China Morning Post has iconic status in the region, with a strong reputation internationally for the quality and credibility of its journalism over the years.'
The agreement includes SCMP Group's other media assets, such as licenses to the Hong Kong editions of Esquire, Elle, Cosmopolitan and Harper's Bazaar.
The deal is certain to raise concerns in Hong Kong, where the South China Morning Post occupies an important position among the English-speaking elite who still dominate the former British colony.
Chinese-language dailies may be more influential than the Post, but changes in its editorial direction are seen as a barometer for press freedom under Chinese rule.
"The SCMP has iconic status in the region, with a strong reputation internationally for the quality and credibility of its journalism over the years," Joe Tsai, executive vice chairman of AlibabaGroup, said in a letter to SCMP readers.
"Like many print media, however, the SCMP faces challenges amid the dramatic changes in the way news is reported and distributed. But these changes play to Alibaba's strengths, which is why we believe the two companies complement each other well."
He added: "In reporting the news, the SCMP will be objective, accurate and fair... day-to-day editorial decisions will be driven by editors in the newsroom, not in the corporate boardroom."
In November, the publisher said it had received a preliminary approach by an unidentified third party interested in its media properties, and media outlets had reported Alibaba was the potential buyer.
Financial terms of the deal were not disclosed.
SCMP has a market value of HK$3.04 billion, or $392 million, according to Thomson Reuters data.
World T20 2016: India and Pakistan in same group
ICC World Twenty20 2016: The full schedule
Why can't Xi shake the Monk's hand?
Bears take a breather; Sensex rallies 216 points led by RIL
Yuan is the 3rd most powerful currency in the IMF basket, what next?