Turkey's Nuri Bilge Ceylan won the Palme d'Or top prize at the this year's Cannes Film Festival for Winter Sleep and dedicated the honour to victims of his country's political strife.
Jury president Jane Campion, the New Zealand filmmaker, handed the trophy to Ceylan, who beat 17 other contenders including David Cronenberg, Jean-Luc Godard and the Oscar-winning director of The Artist, Michel Hazanavicius.
Winter Sleep drew rave reviews as a slow-burn domestic drama that mesmerised audiences despite its more than three-hour length.
Ceylan dedicated the award to the Turkish "youth who lost their lives" in violent anti-government protests that have rocked Turkey over the last year.
Julianne Moore won best actress for her role as a shallow starlet in Cronenberg's biting Hollywood satire Maps to the Stars.
And Britain's Timothy Spall claimed the best actor prize for his role in Mr Turner, a lush historical biopic of 19th century painter JMW Turner by director Mike Leigh. Having won a battle with cancer in the mid-1990s, Spall fought back tears as he thanked the jury, and God "to still be alive".
Bennett Miller, 47, scooped up the best director award for Foxcatcher, a Hollywood film based on the real-life murder of an Olympic wrestler by multimillionaire John du Pont. Critics embraced Miller's third feature film after Capote and Moneyball, and viewers were left particularly stunned by Steve Carell, whose performance as the deranged, sinister du Pont marked a complete turnaround from his previous funny man roles.
"It's really something to be supported and to have people who have faith in you and to come out the other side," Miller said.
The runner-up Grand Prix went to Italian director Alice Rohrwacher, one of two women in competition, for her lyrical look at the rural life of a family of beekeepers, The Wonders.
And the third-place Jury Prize was shared by the oldest and youngest filmmakers in the race, 25-year-old Xavier Dolan for his innovative drama Mommy and Godard, 83, with the 3D extravaganza Goodbye to Language.
Best screenplay went to Leviathan, a harrowing drama assailing abuse of power in today's Russia by Andrei Zvyagintsev.
Winter Sleep marked the first win at the world's biggest cinema showcase for Turkey since 1982, when Yol by Yilmaz Guney shared the gong with Missing by Costa Gavras.
Ceylan had already won awards at Cannes for his previous films Uzak, Climates, Three Monkeys and Once Upon a Time in Anatolia. Bookies had tipped Winter Sleep even before its screening as the favourite to capture the Palme d'Or, based on his track record and a sense that he was due.
Set in Turkey's stunning Cappadocia region, the film stars Haluk Bilginer, known to international audiences from the long-running British soap opera EastEnders He plays a wealthy retired actor living with his much younger, increasingly stifled wife (Melisa Sozen) and his recently divorced sister (popular comic actress Demet Akbag).
Based on short stories by Anton Chekhov, their tense triangle plays out in a quaint hotel serving hikers and motocross enthusiasts who have been drawn to the rugged landscapes.
Trade magazine Variety said Ceylan was "at the peak of his powers" with "a richly engrossing and ravishingly beautiful magnum opus that surely qualifies as the least boring 196-minute movie ever made".
Ceylan later told reporters that while his film dealt more with "human nature" than contemporary politics, his thoughts were with those killed in his country's demonstrations.
"We had a very troubled year last year, and these young people actually taught us a lot of things and some of them sacrificed our lives for our future in a way. So they deserve this dedication I think," he said.
Main prizes at the Cannes Film Festival of 2014
Palme d'Or: Winter Sleep, Nuri Bilge Ceylan
Best Director: Bennett Miller, Foxcatcher
Best Actress: Julianne Moore in Maps to the Stars by David Cronenberg
Best Actor: Timothy Spall in Mr. Turner by Mike Leigh
Best Screenplay: Andrei Zvyagintsev and Oleg Negin for Leviathan
Grand Prix (runner-up to Palme d'Or): The Wonders, by Alice Rohrwacher
Jury Prize: Mommy by Xavier Dolan and Goodbye to Language by Jean-Luc Godard