Just minutes before Smith was named Best Actor at the ceremony, Smith stormed the stage and hit Rock in the face after the comedian made a joke about his wife, Jada Pinkett Smith.
Breaking down in tears as he later accepted his award, Smith used his speech to apologise to both the Academy and his fellow nominees - but not to Rock - as he collected his gong, joking that he “looks like the crazy father.”
But what exactly did he say, and how have people reacted?
Here is everything you need to know about it.
Philadelphia-born Smith, 53, appeared to take offence to a gag Rock made on stage about Jada Pinkett Smith’s short haircut, resulting in him marching on stage to confront the comedian.
Referring to Pinkett Smith’s buzzcut, Rock said: “Jada, can’t wait for GI Jane 2”, prompting the actress to roll her eyes.
However, Smith walked up on stage and appeared to hit Rock before returning to his seat and shouting twice: “Keep my wife’s name out of your f****** mouth.”
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.”
Pinkett Smith has previously spoken about her struggles with alopecia, and said it is what prompted her to shave her head.
What did Will Smith say?
Accepting his Best Actor Oscar for his portrayal of Richard Williams, the father of Venus and Serena Williams, Smith described his character as “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. I’m being called on in my life to love people and to protect people and to be a river to my people.
He added:“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 to have people disrespecting you and you’ve got to smile and pretend like that’s OK.”
Smith’s apologetic acceptance speech in full:
“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 on me to do and be in this world.
“Making this film, I got to protect Aunjanue Ellis, who is one of the most strongest, most delicate people I’ve ever met. I got to protect Saniyya [Sidney] and Demi [Singleton], the two actresses that play Venus and Serena.
“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 gotta be able to take abuse. You gotta be able to have people talk crazy about you. In this business, you gotta be able to have people disrespecting you and you gotta smile and pretend like that’s OK.
“Denzel [Washington] said to me a few minutes ago, ‘At your highest moment, be careful, that’s when the devil comes for you.’ I want to be a vessel for love. I want to say thank you to Venus and Serena … and the entire Williams family for entrusting me with your story.
“That’s what I want to do. I want to be an ambassador of that kind of love and care and concern. 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 the people... and the entire cast and crew of King Richard and Venus and Serena and the entire Williams family.
“Art imitates life. I look like the crazy father, just like they said about Richard Williams! But, love will make you do crazy things.
“To my mother, a lot of this moment is really complicated for me, but to my mother — she didn’t want to come out, she has her knitting friends, she has a knitting crew she’s watching with — being able to love and care for my mother and my family and my wife — I’m taking up too much time — thank you for this honour.
“Thank you for this moment. I thank you on behalf of Richard and Oracene and the entire Williams family. Thank you. I’m hoping the Academy invites me back. Thank you.”
How have people reacted?
Smith, whom he shares two children with Pinkett Smith in Willow and Jaden, recently released a memoir, Will.
The book recalls his experiences of childhood trauma, his relationship with his father and his use of ayahuasca, a psychoactive brew used both recreationally, and for more traditional medicinal purposes.
Smith’s son Jaden tweeted “And That’s How We Do It” after his father appeared to slap Rock.
Jaden later told his Twitter followers his father’s acceptance speech for Best Actor made him cry, adding a selfie of him in a red suit and sunglasses.
Shortly after the incident, Serena Williams shared a video on her Instagram story showing her looking shocked.
In a second clip, the sportswoman admitted she “had to put her drink down”.
Rapper 50 Cent shared a photo of the moment on Instagram and wrote: “B!tch don’t you ever play with me. LOL.”
However, Smith’s actions also attracted criticism from members of the film industry.
The Last Samurai producer Marshall Herskovitz urged the Academy to do more than simply issue a statement in response to the incident.
He said on Twitter: “I call upon the Academy, of which I am a member, to take disciplinary action against Will Smith. He disgraced our entire community tonight.”
Referring to words from Smith’s acceptance speech, English actor Cary Elwes said: “The ‘vessels of love’ I have known or admired never acted violently against another human being…”
A message from the editor:
Thank you for reading. NationalWorld is a new national news brand, produced by a team of journalists, editors, video producers and designers who live and work across the UK. Find out more about who’s who in the team, and our editorial values. We want to start a community among our readers, so please follow us on Facebook, Twitter and Instagram, and keep the conversation going. You can also sign up to our newsletters and get a curated selection of our best reads to your inbox every day.