The other two Oscars for The Departed were best adapted screenplay and best editing.
Best Film: The Departed
Martin Scorsese, The Departed
Forest Whitaker, The Last King of Scotland
Helen Mirren, The Queen
Best Supporting Actor:
Alan Arkin, Little Miss Sunshine
Best Supporting Actress:
Jennifer Hudson, Dreamgirls
Little Miss Sunshine by Michael Arndt
Best Documentary feature film:
An Inconvenient Truth
Best animated feature:
Happy Feet, directed by George Miller
Best Foreign Language film:
Das Leben der Anderen (The Lives of Others), Germany, Canada
Best Live Action short film:
West Bank Story, directed by Ari Sandel
Britain's Helen Mirren was named best actress for her portrayal of the ruling Queen Elizabeth II in The Queen.
The film tells the story of the British royal family in a time of crisis at the death of Princess Diana.
Mirren held her Oscar high in the air and said, "Ladies and gentlemen, I give you the Queen.
"My sister told me 'all kids love to get gold stars,' and this is the biggest and best gold star I've ever had in my life."
Forest Whitaker won best actor playing Idi Amin, the Ugandan dictator, in drama The Last King of Scotland.
Whitaker had to take a moment to calm himself, then with his voice breaking, he remembered a time when he was a young kid watching movies in the backseat of his family's car at the local drive-in theater.
He said that for kids who believe in dreams, he was proof they can come true.
Al Gore, the former US vice president and global warming advocate, painted the Oscars green.
An Inconvenient Truth
|Helen Mirren won best actress for The Queen [EPA]|
, which tells of Gore's 30-year campaign to warn people about global warming, was named the year's best documentary, and singer Melissa Etheridge was given the Academy Award for original song with I Need to Wake Up
"I have to thank Al Gore for inspiring us, inspiring me and showing that caring about the earth is not Republican or Democrat. It's not red or blue. We are all green," Etheridge said.
Meanwhile, newcomer Jennifer Hudson won best supporting actress for her role as spurned singer Effie White in musical Dreamgirls, and veteran Alan Arkin won the Oscar for best supporting actor in Little Miss Sunshine.
While Hudson had been a frontrunner heading into the Oscars, Arkin's was a clear surprise over Eddie Murphy, who had won several other major Hollywood awards this year for his role as a soul singer with a drug habit in musical Dreamgirls.
Mexican film Pan's Labyrinth, a fantasy about a young girl who discovers a violent world in the aftermath of the Spanish Civil War, earned three Oscars for art direction, makeup and cinematography.
Yet, in another surprise it lost the foreign language trophy to Germany's The Lives of Others, which tells of a conflicted Stasi police officer in East Germany.
|The coveted Oscar statuettes [Reuters]|
A musical satire about dueling Arab and Israeli falafel stands in the occupied territories took home an Oscar for best live action short film.
Its title? West Bank Story
"Oh my God," the film's shocked US director, Ari Sandel, said in accepting the award.
"I made a comedy, a musical about Israelis and Palestinians that takes place between two falafel stands in the West Bank. It's a movie about peace and hope."
The title is a play on the Hollywood classic West Side Story about rival New York gangs.
David, an Israeli soldier, falls in love with the beautiful Palestinian cashier Fatima despite the animosity between their families' dueling restaurants and centuries of Middle East conflict.