Cate Blanchet, Kristen Stewart and Salma Hayek were among 82 actresses, filmmakers and producers who stood arm in arm.
The number of protesters represented the 82 films by female directors who have competed for the top Palme d’Or prize since 1946 – compared with the nearly 1,700 male contenders.
“We demand that our workplaces are diverse and equitable so they can best reflect the world in which we live,” said Blanchett in a statement read out with the legendary 89-year-old French director Agnes Varda.
The double Oscar winner said they wanted “a world that allows all of us in front and behind the camera to thrive shoulder to shoulder with our male colleagues”.
The stars walked up the stairs to the Palais des Festivals but stopped halfway to mark the obstacles they face in trying to reach the top.
“The stairs of our industry must be accessible to all. Let’s climb,” Blanchett declared.
The protest took place ahead of the premiere of Girls Of The Sun by Eva Husson, one of only three women out of 21 directors in the running for the Palme d’Or.
The film tells the story of the Kurdish Yazidi all-female Sun Brigade who are fighting Islamic State jihadists in Syria and Iraq, where thousands of women were kept as slaves.
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The demonstration comes seven months after film industry was rocked by allegations of sexual harassment by movie mogul Harvey Weinstein.
It triggered the #MeToo movement which saw Hollywood stars speak publicly for the first time of abuse they have suffered in the business.