Smith won the Academy Award for best actor for his performance in "King Richard."
Only a few minutes earlier, Smith had walked up to the stage and hit presenter Chris Rock in the face with his open hand. Smith reacted after Rock made a joke about Smith's wife, Jada Pinkett Smith.
People in the audience – and television viewers around the world -- were shocked to see the dispute between two well-known performers on Hollywood's biggest night.
Rock's joke related to Pinkett Smith's hairless head. Pinkett Smith has a medical condition that affects hair growth.
Rock said, "Jada, I love you. G.I. Jane 2, can't wait to see it." He meant that Pinkett Smith looked like she was preparing to star in the second G.I. Jane film. The 1997 film was about a woman who enters the military and cuts off her long hair.
After Smith hit Rock's face, he walked back to his seat. He then shouted at Rock to "keep my wife's name out your (blank) mouth." His yelling included a bad word.
In the United States, television viewers did not hear the sound during the dispute. The broadcaster had turned off the sound because of bad language. Viewers in other parts of the world heard the full exchange.
The television broadcast went to an advertisement. Actors Daniel Kaluyya, Denzel Washington and Tyler Perry talked with Smith and calmed the situation.
Not long after, Smith came back to the stage to accept his first Oscar for best actor. He used his acceptance speech to apologize for his earlier actions.
In "King Richard," Smith played Richard Williams, the father of American tennis players Venus and Serena Williams. Smith said in his speech that he, like Williams, "was a fierce defender of his family." He explained that was trying to protect his wife from insult.
Smith added that famous people usually have to "take abuse ... smile and pretend like that's okay."
Smith apologized to the organizers of the Oscars, but he did not apologize directly to Rock. He later said that Denzel Washington told him: "At your highest moment, be careful, because that's when the devil comes for you."
The organization that runs the Oscars is the Academy of Motion Pictures Arts and Sciences. The group said it was against "violence of any form."
Rock did not comment on the incident. Later, the Los Angeles Police Department said Rock had no plans to take legal action against Smith.
The situation became the biggest story of the night, rising past the story of Smith's best actor award and the historic win for "CODA." It became the first film from a streaming media service to win best picture. It also became the first film with a largely deaf cast to win best picture.
See more about the Oscars from VOA's live blog.
I'm Dan Friedell.