Swedish film "The Square", a dark satire of the contemporary art world, was the surprise victor of the top Palme d'Or prize at the world's biggest film festival. The Square, Östlund's fourth feature film to compete at Cannes, is preceded by Force Majeure (2014), Play (2011) and Involuntary (2008), but is the first to compete for the most prestigious prize of all: the Palme d'Or.
"120 Beats Per Minute", a moving drama set in Paris at the height of the AIDS epidemic in the early 1990s, scooped second prize for its wrenching portrayal of a romance between two activists in the advocacy group ACT UP.
"When we have more female storytellers we will have more of the women recognize in my day-to-day life, who are proactive, who have their own agency, don't just react to the men around them, but have their own point of view", she said.
Sofia Coppola took home the award for best director at this year's Cannes Film Festival for her feminist remake of The Beguiled. That was Russia's Yuliya Solntseva, for her film The Story of the Flaming Years, back in 1961.
Chastain, star of The Help said it was "disturbing" to see the way women were depicted on screen.
Joining him on the jury, fellow filmmaker Maren Ade, added: "We need more women making films because we all want this business to reflect modern society and we are still not there".
Nicole Kidman, who starred alongside Colin Farrell in The Beguiled and The Killing of a Sacred Deer missed out on the best actress trophy but was awarded a special prize, collecting the jury's 70th Anniversary Award. She mentioned and thanked Jane Campion for "being a role model and supporting women filmmakers".
Best screenplay: Lynne Ramsay and Yorgos Lanthimos.