Slumdog Millionaire follows a young Indian's life in contemporary Mumbai
Danny Boyle's Slumdog Millionaire has been named best film by the National Board of Review (NBR), the first major prize of the US film awards season.
The body has also released its list of the year's next 10 best films, which includes The Dark Knight and Wall-E.
Clint Eastwood was named best actor for his upcoming drama Gran Torino, while Anne Hathaway won the best actress award for Rachel Getting Married.
The NBR's members include teachers, historians and industry professionals.
It is the first leading body to hand out prizes, although its awards are no guarantee of future success.
However, its best film of 2007 - the Coen brothers' No Country for Old Men - went on to be named best picture at the 2008 Oscars.
Other titles that made the NBR's Top 10 include Brad Pitt fantasy The Curious Case of Benjamin Button and the Coens' comedy Burn After Reading.
NBR TOP 10 OF 2008
Burn After Reading
The Curious Case of Benjamin Button
The Dark Knight
Kazakh epic Mongol: The Rise of Genghis Khan was named best foreign language film, while Man on Wire - about the Frenchman who wire-walked between the Twin Towers - won best documentary.
Supporting actor prizes went to Josh Brolin for his role in Milk, a biopic of gay US politician Harvey Milk, and Penelope Cruz for her work in Woody Allen's Vicky Cristina Barcelona.
Slumdog Millionaire, a Mumbai-set drama from British director Boyle, also won a breakthrough actor award for its young lead Dev Patel.
Its writer, Simon Beaufoy, shared a screenplay award with Benjamin Button scribe Eric Roth.
Pixar's Wall-E, the tale of a robot who falls in love, was named best animated feature.
Slumdog Millionaire has already won top prize at the Toronto Film Festival was named best picture at the British Independent Film Awards last weekend.
The awards season continues next week with the announcement of this year's Golden Globe nominations.