The Paris court dismissed charges against Déborah de Robertis, who has joint French and Luxembourgeois nationality, agreeing with her defence that she was executing a "militant and artistic act" on 24 September when she sat in front of da Vinci's most famous work, flanked by two men and chanting "Mona Lisa! My pussy, my copyright!" through a gilded megaphone.
Déborah de Robertis tweets about her Louvre performance
There was no intent of committing an act of sexual exhibitionism, the judgement said, pointing to the "absence of genital organs" and the fact that "only the pubic hair was visible".
But she was sentenced to 35 hours of community service for having bitten the arm of the jacket of one of the museum attendants who dragged her away, evacuated the room and called the police.
Role of women in art
Saying that her costume was a recreation of one worn by Austrian feminist artist Valie Expert in the 1970s, de Robertis told the court, "It is not sexual nudity I am exhibiting, it's a tool."
Prosecutors had called for an eight-month suspended sentence and the Louvre had joined the case as a plaintiff.
De Robertis was cleared of the same charge by a court in February after appearing semi-nude in two Paris galleries, in one case during an exhibition of Barbie dolls where she said she "to show the body of a real woman".
She also exposed he vagina in front of Gustave Courbet's The Origin of the World, a painting of a vagina, in 2015.
She says her art "questions the place of women in the history of art".
In other art news today: Russian artist detained over Paris bank blaze