Basketball star LeBron James is joining forces with renowned hedge-fund manager John Henry and veteran Hollywood producer Tom Werner in a deal that brings together one of the biggest stars in sports and two of the world's most renowned teams.

The deal between Mr. James and Fenway Sports Group will give Mr. James a minority interest in the soccer club Liverpool, which FSG owns. FSG, which also owns the Boston Red Sox, is partnering with Mr. James's sports-marketing firm, LRMR Branding & Marketing to become the exclusive world-wide...