LeBron James Yachtin' with Jimmy Iovine, Billionaire Boat Club!

LeBron James may not be the richest guy floating off the Amalfi Coast right now ... because Jimmy Iovine just showed up!

The music mogul was spotted on a yacht with LeBron on the 4th of July -- as the NBA star continues to celebrate his new $154 million Lakers contract.

Unclear if LeBron is on Jimmy's yacht ... or if Jimmy is on LeBron's yacht -- but one thing is for sure ... they can both afford some sick boats!

By the way, they have a Beats By Dre connection -- Jimmy (who co-founded the company with Dr. Dre) made a fortune when Apple purchased it for $3.2 billion.

Did you also know ... LeBron ALSO made a ton of cash from the sale? He reportedly got a small stake in the company in exchange for promoting the brand back in 2008 and, when it sold to Apple, he made a cool $30 mil!