Yahoo is poised to sell its core internet business to Verizon Communications for $4.8 billion, sources told The Post on Sunday.

The agreement, slated to be announced early Monday, is expected to end Yahoo Chief Executive Marissa Mayer’s floundering, four-year effort to turn around the once mighty but recently struggling Web pioneer.

The deal would end a lengthy auction that began in February under prodding from activist shareholders led by Starboard Value. It also involves some real estate, sources said.

In grabbing Yahoo, which it will merge with its AOL operation, Verizon beat out rival bidders including Dan Gilbert, founder of Quicken Loans, whose bid had been backed by billionaire Warren Buffett.

Buyout firms TPG, Bain Capital and Vista Equity Partners also were recently in the mix.

The New York-based communications giant won’t be buying Yahoo’s 3,000 technology patents, which could be worth more than $1 billion, and are being auctioned off in a separate process, sources said.

Nor is Verizon buying Yahoo’s stake in Yahoo Japan or its equity chunk of China-based Alibaba.

Officials at Yahoo and Verizon declined to comment.

Verizon will add Yahoo’s news, sports and finance sites to its Web titles like Huffington Post and TechCrunch, which it scooped up last year with its $4.4 billion purchase of AOL.

Headed by former Google exec Tim Armstrong, AOL is likewise licking its chops for Yahoo’s advertising tech tools, as well as its search engine and e-mail service.

Armstrong, who had tried and failed to convince Mayer to buy AOL in 2014 before selling to Verizon, will create the third-largest internet advertiser with the Yahoo deal — albeit far behind Google and Facebook, which together control more than half of the online advertising market, according to eMarketer.

AOL and Yahoo account for just 3.4 percent and 1.8 percent, respectively, of the $69 billion niche, eMarketer said.

Yahoo disclosed last week that its second-quarter revenue minus the cost of commissions paid for Web traffic tumbled 19 percent from the year-earlier period. Yahoo also admitted its $1.1 billion 2013 acquisition of Tumblr has lost nearly two-thirds of that value.

With Yahoo’s core business sold off, the Sunnyvale, Calif., firm founded in 1994 by Jerry Yang and David Filo must now decide what to do with its Yahoo Japan and Alibaba stakes.

Yahoo owns about 35 percent of Yahoo Japan and 15 percent of Alibaba, two overseas companies that have long dwarfed Yahoo in size.

Together, the two stakes account for the lion’s share of Yahoo’s $36 billion market capitalization.