The two women were joined by a range of others from the worldwide film community - fellow jury members Kristen Stewart and Ava DuVernay, actresses Salma Hayek and Marion Cotillard, directors Patty Jenkins and Haifaa Al Mansour, and CAA talent agents Hylda Queally and Maha Dakhil.
"We hope that Cannes will welcome these new initiatives", said Fremaux.
Their signatures hit the page just two days after 82 female film industry figures staged a red-carpet protest at the world-famous French film festival, demanding an end to gender imbalance in the film industry. "We hope that it will reinforce the realization that the world is not the same anymore".
Also joining were the five female members of this year's Cannes jury: Cate Blanchett, Kristen Stewart, Ava DuVernay, Lea Seydoux and Burundian singer Khadja Nin. In the years since, she noted, 1,688 male directors have made the same trek. "The world has changed".
The pledge was drawn up by the French gender equality group 50/50 en 2020, along with members of the Time's Up movement.More news: UFC 224: Lyoto Machida Reminds Folks & Michael Bisping His Kicks "Retire People"
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Cannes has come under increasing scrutiny in recent years over the number of female directors selected into its main slate, considered one of the most esteemed achievements in cinema. The prestigious Palme d'or has been bestowed upon 71 male directors - too numerous to mention by name - but only two women - Jane Campion, who is with us in spirit, and Agnès Varda who stands with us today.
Of the 21 films in competition this year, three are directed by women.
The protest was held ahead of the premiere of French filmmaker Eva Husson's "Girls of the Sun", which is about a Kurdish battalion of women soldiers.
The Cannes Film Festival has always been criticized for gender imbalance on its juries and in its film selection. The move comes as the topics of inclusion and equality have been front and centre here.
After the signing, filmmaker Rebecca Zlotowski noted it was Blanchett's birthday, and attendees serenaded the actress with a rendition of "Happy Birthday".