Best actor nominee Will Smith has smacked presenter Chris Rock in the face with an open hand and shouted a vulgarity at the comedian for making a joke about his wife's appearance at the Oscars ceremony.

Rock made a joke about the hairstyle of Smith's wife Jada Pinkett Smith that referenced the movie G.I. Jane, in which actress Demi Moore shaved her head.

Smith, who is nominated for best actor for King Richard, stormed onto the stage and slapped Rock in what at first appeared to be a scripted joke.

But the mood turned sombre moments later when Smith, back in his seat, shouted back, "Keep my wife's name out of your f***ing mouth".

A clearly shaken Rock went on to present the award for best documentary feature to Summer of Soul (Or, When The Revolution Could Not Be Televised).