Gus Van Sant's film Elephant, based on the 1999 Columbine school shootings, has won the Palme d'Or prize and best director honour at Cannes film festival.
Sant said he wanted to observe the teenage students' lives
Van Sant, who also directed the Oscar-winning Good Will Hunting, used high school students rather than actors in his film.
"Thank you very much, from the bottom of my heart. Vive la France!" he said.
He was the first American to win the prestigious prize
since Quentin Tarantino did for Pulp Fiction in 1994.
"I thought I was finished," he added. "I've been trying to get my films to Cannes for years, and
this time, it's wonderful to receive such a prize. To win is miraculous and fortunate and lucky."
The Palme d'Or was awarded by the festival's jury, which was headed by French director Patrice Chereau and included Oscar-winning director Steven Soderbergh and actresses Meg Ryan and Aishwarya Rai.
Elephant's young cast were not professional actors
The director beat other favourites for the prize including Dogville, starring Nicole Kidman, and Clint Eastwood's star-studded Mystic River, both of which left empty-handed.
British director Peter Greenaway's film, The Tulse Luper suitcases also missed out on a prize, having been up for the Palme d'Or.
Van Sant rejected any suggestion that his movie was anti-American.
"I live in America, it's made from the viewpoint of my own life in America," he said.
Samira Makhmalbaf, 23, won the Jury prize
But he did admit the film criticised certain things, including "the urge to conform in a bland way, forgetting diversity, which is encouraged at Cannes".
Iranian director Samira Makhmalbaf, 23, won the Jury Prize for At Five in the Afternoon (Panj E Asr), which looks at the plights of surviving post-Taleban Afghanistan.
She also used a cast of amateurs in her low-budget film which focuses on an Afghan woman, Nogreh, who is desperate to shake off the constrictions of the old regime in a cash-starved land.
Young Canadian actress Marie-Josee Croze, who plays a drug addict in The Barbarian Invasions, won best actress for her role in a film about a man in
his 50s dying of cancer.
The film's director, Denys Arcand, also won best screenwriter.
And best actor was shared by the stars of Turkish film Distant (Ukak), Muzaffer Ozdemir and the late Mehmet Emin Toprak.
Dogville, starring Nicole Kidman, left empty-handed
Toprak died in a car crash shortly after making the film, which focuses on the emotional isolation experienced by a photographer whose feels invaded when a jobless relative invades his privacy.
The film, directed by Nuri Bilge Ceylan, also won the Grand Prize.
The competition selection this year has proved disappointing, with Screen Daily's Allan Hunter saying the "choices were considered the worst in living memory".
Gallo's Brown Bunny, starring Chloe Sevigny, got a bad reception
Cannes has suffered a 7% drop in guests from the US although there has been a large presence of Hollywood actors including Keanu Reeves, Arnold Schwarzenegger and Kidman.
The Hollywood Reporter said it was likely that "Cannes 2003 will go down as a soft market for American dealmakers".
Meanwhile Vincent Gallo, director and star of the controversial film Brown Bunny screened in competition this week, reportedly apologised for the movie after it received a disastrous reception from critics.
The film, which features an extended explicit sex scene, has been damned as pretentious and self-indulgent.
At Five in the Afternoon focuses on post-Taleban plight
"I thought that I was compelled by something beautiful that I could share with other people," he is reported to have said in Screen International.
"I'm disappointed that people aren't responding to it in that way. I can only apologise to the people who feel they've wasted their time," the trade weekly added.
Last year's winner at Cannes, The Pianist, directed by Roman Polanski, went on to have great success at the 2003 Oscars, winning best director and best actor.