Dark drama Joker about the origins of the villainous character has won the Golden Lion award at the Venice Film Festival, while Roman Polanski's military drama about France's notorious Dreyfus affair has taken the runner-up prize.
Joaquin Phoenix, who won rave reviews at the festival, plays DC Comics superhero Batman's nemesis, and the story follows his transformation from vulnerable loner to confident villain.
Joker distances itself from typical superhero films, with sombre lighting and dark music throughout.
"I want to thank Warner Bros and DC for stepping out of their comfort zone and taking such a bold swing on me and this movie," director Todd Phillips said in his acceptance speech on Saturday, also thanking Phoenix for trusting him with his "insane talent".
"There is no movie without Joaquin Phoenix ... Joaquin is the fiercest and bravest and most open-minded lion that I know."
The film was generating awards buzz even before Venice. The festival is considered a launch pad for the awards season, having premiered Oscar winners like Roma and Birdman.
In a surprise move, Polanski's An Officer and a Spy took the Silver Lion Grand Jury Prize.
At a time of #MeToo and with only two female directors out of 21 in the competition line-up, festival organisers had faced criticism for including Polanski's work in the program due to renewed controversy over his conviction for a sex crime.
They defended the move, saying it was the film, not the man, being judged. Jury member Paolo Virzi told a news conference the judges had solely focused on the movie in their discussions.
Polanski pleaded guilty in 1977 to having unlawful sex with a 13-year-old girl in Los Angeles. He fled the United States in 1978 for fear a deal for leniency with prosecutors would be overruled and he would get a lengthy prison term. Aged 86, he now lives in Europe.
The French-Polish director, who was expelled from the Academy of Motion Picture Arts and Sciences last year, did not travel to Venice. His wife Emmanuelle Seigner, who stars in the film, collected the award on his behalf.
"He is very happy and I am convinced this is a very important movie for him, it will give him a lot," she told reporters.
Australian Associated Press