Isiah Thomas was furious when he saw his 1984 NBA All-Star Game MVP trophy hit the auction block recently — claiming it’s “stolen” property that was heisted from his old high school.

The trophy itself is a pretty cool item — Thomas won the award after posting 21 points, 5 rebounds and 15 assists while playing against guys like Magic Johnson and Kareem Abdul-Jabbar.

Thomas says he allowed the trophy to be displayed at his old high school in Illinois, but claims it was stolen back in June 2019.

So, when he saw it up for auction with the Heritage Auctions website, Thomas was not pleased.

“This trophy was stolen from St. Joseph High School the night Mr. Pingatore my coach died,” Thomas posted on Twitter … “It belongs to me.”

“You stole my trophy please return it! Let it be known.”

Heritage Auctions responded to Thomas — saying, “We take the concerns and allegations of Mr. Thomas very seriously. We will investigate them as expeditiously as possible.”

A rep for the auction house tells us the item was “immediately removed” — noting, “We are working at this very moment to find out the real story behind this trophy.”

In the meantime, watch the highlights of Thomas from the game … dude was BALLIN!!!