Jeff Yass, the billionaire Wall Street financier and Republican megadonor who is a major investor in the parent company of TikTok, was also the biggest institutional shareholder of the shell company that recently merged with former President Donald J. Trump’s social media company.

A December regulatory filing showed that Mr. Yass’s trading firm, Susquehanna International Group, owned about 2 percent of Digital World Acquisition Corp., which merged with Trump Media & Technology Group on Friday. That stake, of about 605,000 shares, was worth about $22 million based on Digital World’s last closing share price.

It’s unclear if Susquehanna still owns those shares, because big investors disclose their holdings to regulators only periodically. But if it did retain its stake, Mr. Yass’s firm would become one of Trump Media’s larger institutional shareholders when it begins trading this week following the merger.

Shares of Digital World have surged about 140 percent this year as the merger with the parent company of Truth Social, Mr. Trump’s social media platform, drew closer and Mr. Trump became the presumptive Republican nominee for president.

“Susquehanna is a market maker and has zero economic interest in Trump Media,” said the company in a statement. “The firm’s long position is offset by short positions of the same size.”

Regulatory filings show the firm used offsetting securities to try to minimize its gains or losses in the stock.