The not quite 6-year-old Huffington Post was co-founded by Editor in Chief Arianna Huffington, who will become president and editor-in-chief off The Huffington Post Media Group, AOL said.
The unit will include all Huffington Post and AOL content, including Engadget, TechCrunch, Moviefone, MapQuest, Black Voices, PopEater, AOL Music, AOL Latino, AutoBlog, Patch and StyleList, the company said.
"The acquisition of The Huffington Post will create a next-generation American media company with global reach that combines content, community, and social experiences for consumers," said Tim Armstrong, AOL's chairman and chief executive officer.
"Arianna is a singularly passionate and dedicated champion of innovative journalistic engagement, and a master of the art of using new media to illuminate, entertain and enhance the national conversation."
For her part, Huffington called the deal "a merger of visions and a perfect fit for us."
"The Huffington Post will continue on the same path we have been on for the last six years -- though now at light speed -- by combining with AOL," she said. "We are fusing a legendary and powerful new media brand with a vibrant, innovative news organization, known for its distinctive voice, a highly engaged audience, an expertise in community-building, and a track record for demystifying the news and putting flesh and blood on the data while drawing our audience into the conversation."
The Post has about 25 unique visitors per month, which will bring AOL's U.S. total to 117 million unique visitors and 270 million worldwide, the company said.