Fenway Sports Management, which bought Liverpool last year for $488 million, is headed by hedge fund manager John Henry and Hollywood producer Tom Werner and also owns the Boston Red Sox and regional cable sports broadcaster NESN.
The deal aligns James's sports marketing firm, LRMR Marketing & Branding, with FSM, the company said in a statement.
"FSM will work with LRMR on James's future business, marketing, endorsement and philanthropic endeavors all over the globe," it said. "The partnership between FSM and LRMR will be the exclusive avenue worldwide for the pursuit of opportunities to be associated with LeBron James."
As part of the deal, James also will get a minority stake in the Liverpool Football Club, the company said.
"We're not interested in talent or athlete representation but we think he is one of the most remarkable athletes of his time," Werner told The Wall Street Journal. "We believe we can open doors for LeBron and LeBron can open doors for us."
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