The defeat ended Williams’ bid for a record-equalling 24th Grand Slam title.
“It was a big error day for me today,” the 39-year-old told reporters after the match at Rod Laver Arena.
Asked if it was just a bad day at the office, Williams said: “I don’t know. I’m done,” before leaving the room in tears.
Great recognizes great.Thanks for treating us to that brilliant battle, @serenawilliams & @naomiosaka 👏#AusOpen… https://t.co/YWtDOWOAAU
— #AusOpen (@AustralianOpen) 1613622910000