Eighty-two women participated in the protest against gender inequality in the film industry.
The number symbolizes how many movies made by female filmmakers have been chosen as official selections at the festival since it began in 1946.
More than 1,600 films helmed by men have competed at the festival over the years.
Blanchett and Agnes Varda took turns reading out a statement, explaining their position.
Varda and Jane Campion are the only women filmmakers to ever win the festival's prestigious Palme d'Or.
"Women are not a minority in the world, yet the current state of our industry says otherwise," said the statement Varda and Blanchett read.
"As women, we all face our own unique challenges, but we stand together on these stairs today as a symbol of our determination and commitment to progress. We are writers, producers, directors, actresses, cinematographers, talent agents, editors, distributors, sales agents and all involved in the cinematic arts. We stand in solidarity with women of all industries."
Blanchett is the president of this year's festival jury.
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