Kyrie Irving hooked up a homeless fan with more than $240 IN CASH before playing the Rockets in Houston on Thursday -- and the reaction is INCREDIBLE!!!

The guy who shot the video, Thomas Moreno, tells us ... the Boston Celtics superstar was walking to the team bus when he was approached by a man who was telling people he was destitute.

Kyrie stopped and chatted with the guy ... and then, the big moment happened -- Irving reaches into his pocket, pulls out the cash and hands it right to his new friend.

BOOM!!!!

The guy was so happy, he literally jumped for joy and started hugging random people! He also chased after Kyrie to thank him for the generous gift.

We reached out to Kyrie and the Boston Celtics for comment -- but so far, haven't heard anything.

But, the video basically speaks for itself.