The festival, which runs Oct. 22-31 in the Italian capital, will host the world premiere of "8," a U.N.-backed movie on poverty made of eight segments by different directors including Jane Campion and Wim Wenders.
The film, screening out of competition, aims to raise awareness of world poverty. It is inspired by the U.N.'s Millennium Development Goals which were adopted by world leaders in 2000 to cut poverty and disease and improve health care and education for the world's poor by 2015.
But halfway through the deadline, not all countries have met those goals.
The stories focus on Africa, the U.S., Australia, Iceland, Germany and the Amazon rain forest, organizers said. Gael Garcia Bernal, Gus Van Sant, Mira Nair, Jan Kounen, Abderrahmane Sissako and Gaspar Noe are also among the movie's directors.
The festival will also screen out of competition Saul Dibb's historical pageant "The Duchess," starring Ralph Fiennes and Knightley as the spirited and unconventional Georgiana, duchess of Devonshire, an 18th-century ancestor of Princess Diana.
Among the 20 movies competing for the Best Movie Award are U.S. police drama "Pride and Glory" by Gavin O'Connor, starring Edward Norton, Colin Farrell and Jon Voight and a French-Cambodian film, "Un Barrage contre le Pacifique" (The Sea Wall), a screen adaptation of the novel by Marguerite Duras, starring Isabelle Huppert.
Also competing is "Easy Virtue," a 1920s period comedy with Ben Barnes as a young man who shocks his upper-crust English family by bringing home his American bride, played by Jessica Biel. Colin Firth and Kristin Scott Thomas also star in the movie.
Al Pacino is expected to come to pick up an acting award and take part in public meetings and conferences, organizers said. Director David Cronenberg will also attend.
The festival - mainly held at the city's Auditorium, an exhibition and concert center designed by architect Renzo Piano - also features a section dedicated to movies for or about children and teenagers.
By MARTA FALCONI