Will Smith slaps Chris Rock for joke about wife Jada in a shocking moment.She has alopecia, according to People magazine, a disease which causes hair loss.

 Will Smith, who is up for a best actor award, got up on stage and appeared to smack presenter Chris Rock, who made a joke about the actor’s wife.

Rock had said Smith’s wife, Jada Pinkett Smith, was going to be in the next “G.I Jane” movie, a reference to her lack of hair.

Although ABC went silent for the exchange, Smith could be heard saying “Keep my wife’s name out of your f-ing mouth

When Will won the Best Actor award, he said in his speech, “I'm gonna apologise to the Academy. I'm gonna apologise to my fellow nominees

Twitter has reacted to the episode. “What just happened with chris rock and will smith,” asked a fan. “Lmaoooo wait a minute. Will Smith slapped the sh*t out of Chris Rock,”

Last year, Jada had released a video on Instagram to talk about a new patch of baldness caused by alopecia, “Look at this line right here,” Jada, 50, said, as she showed her scalp to the camera.

Will won in the Best Actor category for his performance in King Richard. He plays the father of tennis legends Venus and Serena Williams in the movie.