Smith walked up on stage and appeared to hit Rock before returning to his seat and shouting: “Keep my wife’s name out of your f****** mouth.”
*Please note, some of the audio in the video on this article has been muted due to strong language, and the footage contains some violence.*
Rock appeared shocked and flustered as he tried to resume presenting the best documentary feature category.
He said: “That was the greatest night in the history of television.”
Smith, who later won the Oscar for best actor, apologised to the Academy, but not to Chris Rock.
Accepting his best actor Oscar for his portrayal of Richard Williams, the father of Venus and Serena Williams, Will Smith said: “Richard Williams was a fierce defender of his family.
“In this time in my life, in this moment, I am overwhelmed by what God is calling me to do and be in this world.”
He added: “I’m being called on in my life to love people and to protect people and to be a river to my people.
“I know to do what we do you’ve got to be able to take abuse, you’ve got to be able to have people talk crazy about you in this business.
“You’ve got to be able have people disrespecting you and you’ve got to smile and pretend like that’s OK.
“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.”
The Academy has said it “does not condone violence of any form” following an altercation during the 94th annual ceremony between best actor winner Will Smith and comedian Chris Rock.
“The Academy does not condone violence of any form,” the organisation tweeted.
“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.”
The Los Angeles Police Department (LAPD) says no police report has yet been filed following an altercation at the 94th Academy Awards, during which Oscar-winner Will Smith slapped comedian Chris Rock.
“LAPD investigative entities are aware of an incident between two individuals during the Academy Awards programme,” an LAPD spokesperson told the PA news agency.
“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.”