EBay may want to slim down to boost its stock price.

That, at least, is according to Paul Singer’s Elliott Management, which argued Tuesday that a spinoff or sale of its StubHub and classifieds businesses could cause the company’s stock to more than double to $63 a share.

EBay shares soared as much as 12 percent on news of Elliott’s stake after falling more than 20 percent over the past year. Recently they were up roughly 8 percent at $33.41 in midday trades Tuesday.

The $34 billion hedge fund argues that eBay has been “distracted” by these non-core endeavors while rivals — both large and small — have gained market share in the San Jose, Calif.-based company’s core online retail business.

“As the broader internet universe has flourished, especially e-commerce peers, eBay’s stock has floundered,” Jesse Cohn, partner at Elliott, said in a letter to eBay’s board, pointing to upstarts such as The RealReal and Etsy.

On top of Elliott’s 4 percent stake in eBay, Cohn has some skin in the game. He noted that eBay provides a way for “millions of sellers” to earn a living — including his mother, who has been selling jewelry on eBay for more than 10 years.

Following a sale or spinoff of the noncore business — which together could reap as much as $16.5 billion — Elliott argues eBay should focus on revitalizing its marketplace, pointing to “countless technical issues” users have complained about, such as incorrect billing and lost photos.

“The consistent reliability of the platform is central to eBay’s success, and management must do all that it takes to achieve it,” Cohn wrote.

Meanwhile, Elliott may not be the only activist nipping at eBay. The Wall Street Journal reported early Tuesday that Jeff Smith’s Starboard Value also has a stake in eBay and has been speaking with management over the last few months.

Reps from Starboard did not immediately respond to requests for comment.

EBay acknowledged Elliott’s investment Tuesday.

“We appreciate Elliott’s recognition of the strength and power of eBay’s business and will carefully review and evaluate Elliott’s proposals. We look forward to the opportunity to engage with Elliott, as we do with all shareholders,” the company said.