The actor, who went on to win Best Actor later on Sunday evening, appeared to take offence to a gag Rock made about Jada Pinkett Smith’s short haircut.
The Magic Mike XXL star and Red Table Talk host has previously spoken about her experiences with hair loss and said her struggle with alopecia is what prompted her to shave her head.
Speaking on Instagram last year, the actress explained: "Now at this point, I can only laugh… y’all know I’ve been struggling with alopecia. Just all of a sudden, one day…it just showed up like that.
"Now, this is going to be a little bit more difficult for me to hide.
“So, I thought I’d just share it so y’all not asking any questions…Mama’s gonna have to take it down to the scalp so nobody thinks she got brain surgery or something.
“Me and this alopecia are going to be friends … period!"
What did Chris Rock say?
Referring to Pinkett Smith’s buzzcut, Rock said: “Jada, can’t wait for GI Jane 2”, to which the actress rolled her eyes.
The comedian’s joke was a reference to the 1997 movie G.I Jane, starring Demi Moore sporting a buzzcut similar to Jada’s.
However, the comment prompted Will to walk up on stage where he slapped the presenter, before returning to his seat.
Rock appeared shocked and flustered by the incident as he tried to resume presenting the best documentary feature category.
He said: “Wow. Will Smith just smacked the s**t out of me.”
Smith then responded by shouting twice: “Keep my wife’s name out of your f****** mouth.”
Rock replied: “I’m going to, okay?
“That was the greatest night in the history of television.”
Rock handed the prize to The Roots star Ahmir ‘Questlove’ Thompson for his film Summer Of Soul.
After leaving the stage, Sean ‘Diddy’ Combs appeared and said: “Will and Chris, we’re gonna solve that like family at the gold party.”
Will Smith later went on to win the best actor award for his performance in King Richard, the American biographical sports drama film about the father and coach of tennis players Venus and Serena Williams.
Accepting his award, Smith apologised for his earlier outburst and said: ““Richard Williams was a fierce defender of his family.
“I want to apologise to the Academy, I want to apologise to all my fellow nominees.
“This is a beautiful moment and I’m not crying for winning an award, it’s not about winning an award for me, it’s about being able to shine a light on all of the people.”
He continued: “Art imitates life, I look like the crazy father, just like they said about Richard Williams, but love will make you do crazy things.”
After paying tribute to his mother and his family he added: “Thank you for this honour, thank you for this moment…I hope the Academy invites me back.”
Smith won’t face police charges
Chris Rock has declined to file a police report, the Los Angeles Police Department (LAPD) has confirmed.
A full statement from the police force said: "LAPD investigative entities are aware of an incident between two individuals during the Academy Awards program.
"The incident involved one individual slapping another. The individual involved has declined to file a police report.
“If the involved party desires a police report at a later date, LAPD will be available to complete an investigative report."
The Academy also broke its silence on the matter, stating it “does not condone violence of any form”.
In a statement on social media, the organisation said: “The Academy does not condone violence of any form.
"Tonight we are delighted to celebrate our 94th Academy Awards winners, who deserve this moment of recognition from their peers and movie lovers around the world."