Jayson Tatum Gets 5-Year $315 Million Extension, Biggest Deal In NBA History

Jayson Tatum's summer just got even better -- the Boston Celtics champion just secured a 5-year, $315 MILLION extension ... making it the biggest contract in NBA history.

News of the negotiations broke minutes ago ... with the 26-year-old agreeing to a supermax deal to stay put in Beantown -- quite possibly the biggest no-brainer of the offseason.

Tatum is fresh off winning his first title with the Cs after eliminating the Dallas Mavericks in Game 5 of the NBA Finals last month ... and while he didn't win MVP honors, he was crucial to Boston's success this postseason -- averaging 25 points, 9.7 rebounds and 6.3 assists a game.

The huge payday will start in the 2025-26 season ... with Tatum slated to make $54 million. It will increase roughly $4-5 milli each year, which means he'll rake in a whopping $71 million in 2029-30.

Tatum has emerged as one of the best players in the league after going No. 3 overall to the Celtics in 2017 ... and finished sixth in regular season MVP voting this past season.