Academy of Motion Picture Arts and Sciences president Sid Ganis announced the decision at a press briefing at the Academy headquarters.
"After more than six decades the Academy is returning to some of its earlier roots when a wider field competed for the top award of the year," he said.
"The final outcome, of course, will be the same -- one best picture winner -- but the race to the finish line will feature ten, not just five, movies from 2009."