Helen Mirren and Ben Affleck took the top acting awards.
Mirren was named best actress for her portrayal of Queen Elizabeth II in Stephen Frear's "The Queen." Affleck won best actor for his role in Allen Coulter's "Hollywoodland," which dramatizes an investigation into the death of George Reeves, star of the 1950s TV show "Adventures of Superman."
"The Queen" also took the prize for best script.
Chinese director Jia Zhang-ke's "Still Life" or "Sanxia Haoren" was a surprise entry late in the festival, and trumped candidates like Emilio Estevez' "Bobby," about the assassination of Robert Kennedy, and "The Queen," about the week that followed Princess Diana's death.
"Still Life" was shot in the old village of Fengjie, which has been destroyed by the building of the Three Gorges Dam, and tells of people who go back there.
More than 1.13 million Chinese have been relocated to make way for the dam, many of them complaining of bleak prospects in their new homes above the waterline or in other parts of China.
"We were told there would be a surprise film at the end of this festival, and we didn't have a lot of discussion," French actress Catherine Deneuve, who headed the jury that awarded the top prize, told reporters after the ceremony.
"The beauty of the cinematography and the quality of the story, without getting political, the characters, we were very touched and we were very moved," Deneuve added. "We know it's a very special film."
The Silver Lion for directing went to Alain Resnais for his film "Private Fears in Public Places." Resnais returned to the Venice Film Festival 45 years after his film "Last year at Marienbad" won the Golden Lion.
Resnais' new film is an adaptation of British playwright Alan Ayckbourn's play of the same name, and tells the overlapping stories of six people's search for identity, spun around alcohol, sex and religion.
The movie "Nuovomondo" ("Golden Door") won the Silver Lion for revelation, an award that the jury does not have to hand out. The movie follows the voyage of a Sicilian family in the early 1990s from their homeland to America.