Cate Blanchett who headed the film festival’s jury of five women and four men said that it had been “bloody hard” to select a winner.
“But in the end I think we were completely bowled over by how intermeshed the performances were with the directorial vision,” she said of Shoplifters.
US director Spike Lee received the runner-up Grand Prix for BlacKkKlansman, based on the true story of an African-American police officer who managed to infiltrate the Ku Klux Klan.
Blanchett said the film, which explicitly links the 1970s tale and white nationalism in the Donald Trump era, “blew us out of the cinema”.
Nadine Labaki, a female director from Lebanon, won the Jury Prize – effectively the bronze medal – for Capharnaum, a realist drama about childhood neglect in the slums of Beirut.
Italian actress Asia Argento used a speech at the ceremony to take aim at the film industry as she labelled Cannes Harvey Weinstein’s “hunting ground”.
Argento, who has said she was raped by Weinstein at Cannes in 1997 when she was 21, took the microphone and vowed to fight for justice for other victims.
“Even tonight, sitting among you, there are those who have still to be held accountable for their conduct against women,” she said.
“You know who you are. But most importantly we know who you are. And we’re not going allow you to get away with it any longer.”
She added: “I want to make a prediction. Harvey Weinstein will never be welcomed here ever again. He will live in disgrace, shunned by a film community that once embraced him and covered up for his crimes.”
Weinstein has denied allegations of non-consensual sex. A spokesman for Weinstein had no immediate comment.
Minutes before Argento took the stage police in Paris said they had opened a criminal probe against one of France’s best-known directors, The Fifth Element maker Luc Besson, for allegedly raping an actress.
The 27-year-old woman claims Besson drugged her before the alleged incident at a hotel in Paris, a judicial official said.
The director reportedly denies wrongdoing after the complaint was made on Friday.
More from cannes film festival
Cate Blanchett to lead 2018 Cannes film festival jury
Jessica Chastain ‘disturbed’ by Cannes’ portrayal of women
Cannes 2017: Crowning the new King and Queen
Emoji movie crashes Cannes Film Festival party
Netflix at Cannes: One step forward, two steps back
Roman Polanski film to open at Cannes film festival
The full list of prize-winners at the 71st Cannes film festival:
:: Palme d’Or: Shoplifters by Hirokazu Kore-Eda (Japan)
:: Grand Prix: BlacKkKlansman by Spike Lee (US)
:: Jury Prize: Capernaum by Nadine Labaki (Lebanon)
:: Special Palme d’Or: Jean-Luc Godard (France, Switzerland) for The Image Book
:: Best director: Pawel Pawlikowski (Poland) for Cold War
:: Best actress: Samal Yeslyamova (Kazakhstan) for Ayka
:: Best actor: Marcello Fonte (Italy) for Dogman
:: Best first film: Girl by Lukas Dhont (Belgium)
:: Best short film: All these Creatures by Charles Williams (Australia)
:: Special mention for short film: On The Border by Wei Shujun (China)
:: Best screenplay (tied): Director Alice Rohrwacher (Italy) for Happy As Lazzaro and director Jafar Panahi (Iran) and scriptwriter Nader Saeivar (Iran) for Three Faces