LeBron James -- Props From Obama ... 'Happy for King James'

Didn't take long for President Obama to weigh in on the NBA Finals -- with POTUS taking to Twitter to dap up LeBron and the Cavs for shocking the Warriors in Game 7.

"What a game and what a series for the @Cavs," Obama tweeted roughly an hour after the game ... "Happy to see @KingJames bring it home for Cleveland!"

LeBron reacted to the tweet live on NBA TV.