An "ultra-rare" signed rookie card for four-time National Basketball Association (NBA) champion LeBron James sold for $5.2 million on Monday, breaking the record for the most expensive basketball card ever sold.

It also equaled the record for any sports trading card, matching the amount paid in January for a 1952 rookie card for baseball great Mickey Mantle.

"At the heart of every collector in 2003 was the hope of pulling the ultra-rare LeBron James Rookie Patch Auto Parallel numbered to 23 copies," PWCC Marketplace said in a statement posted to social media.

"With so few ever becoming available and demand increasing by the day, this card is quickly becoming the crown jewel of all sports card investing."

The buyer's identity was not immediately made public.

A transformative figure on and off the court, 36-year-old James is widely considered among the greatest ever to play the game, earning NBA most valuable player honors four times.

The 17-time All-Star added yet another accolade to his dazzling career last year, picking up his fourth NBA Finals MVP title after helping his Los Angeles Lakers win the championship over the Miami Heat.

Ultra-wealthy sports fans dived into the sports memorabilia market with renewed vigor this year, with a signed rookie card for seven-time Super Bowl winner Tom Brady selling for $2.25 million earlier this month and a rare Kobe Bryant rookie card selling for $1.795 million in March.

(Reporting by Amy Tennery; editing by Jane Wardell)