Kyrie Irving clapped back at a fan and now it's going to cost him -- the NBA just fined the Nets star $25,000 for his "motherf***er" retort in a game on Monday.
The league announced the punishment on Thursday afternoon ... saying in a statement they levied the fine "for directing obscene language toward a fan."
The incident took place during Brooklyn's game against the Cavaliers in Cleveland ... when in the second quarter of the Nets' 114-107 loss, a fan appeared to ask Irving, "Kyrie, you need LeBron?"
Check out the clip ... you can hear Irving fired back at the troll by saying, "I got ya'll a championship and ya'll motherf***ers still ungrateful."
The back and forth between the hecklers and Kyrie continued ... as another fan appeared to yell, "It was just one. It was just one."
Irving -- who is only allowed to play in the team's road games due to his vax status -- then told the crowd, "Keep it, keep it. Save it."
It's not hard to see why Irving had an issue with the heckling in Cleveland -- after all, he averaged 27.1 points in the 2016 NBA Finals and helped deliver (alongside LeBron James) Cleveland its first major sports championship in 52 years at the time.