The purchase is part of a wider deal between BuzzFeed and Verizon Media, according to the Wall Street Journal.
The two companies will reportedly explore joint advertising opportunities and syndicate content on each others platforms.
Verizon Media will get a minority stake in BuzzFeed and also make a cash investment in the company.
BuzzFeed founder and CEO Jonah Peretti will reportedly run the newly combined media company.
In a joint statement, the companies said BuzzFeed and HuffPost have complementary audiences and will benefit from greater scale.
BuzzFeed will carry out the search for a new editor-in-chief for HuffPost, which was launched by Arianna Huffington in 2005, and was known as the Huffington Post until 2017.
The Huffington Post was sold to AOL in 2011 for $315m, and mobile phone network Verizon acquired it when it bought AOL for $4.4bn in 2015.