By Hanna Rantala
ROME (Reuters) - A shrunken Matt Damon will open the 74th Venice Film Festival, organizers said on Thursday when they unveiled the line-up for an event that often gives an early glimpse of Oscar contenders.
Alexander Payne's "Downsizing", a satire about a couple who decide to shrink themselves to four inches tall, opens the festival next month, with Kristen Wiig and Christoph Waltz starring alongside Damon.
It will compete for the Golden Lion against 20 other movies including Guillermo Del Toro's "The Shape of Water" and the unexpected addition of Darren Aranofsky's "Mother!", a horror starring Jennifer Lawrence.
"(Distributor) Paramount was very much in doubt over whether to present the film at a festival in order not to make any spoilers," festival director Alberto Barbera told a news conference in Rome.
Another hotly-anticipated entry is "Human Flow", a documentary about the global refugee crisis by Chinese artist Ai Wei Wei.
Barbera said he was "very satisfied" with the line-up.
"There are only maybe two or three films that we ... wanted to have for the festival and we couldn't," he said.
Damon reappears in "Suburbicon", a dark comedy directed by George Clooney that also stars Julianne Moore.
Moviemakers will be hoping for a replay of the success of films such as "La La Land", "Gravity" and "Birdman" which went from Venice launches to Academy Awards glory.
The world's oldest film festival will also stage what organizers say is the first virtual reality competition at a major cinema event.
Outside of the competition, Stephen Frears will present "Victoria and Abdul", his latest work on the British monarchy, with Judi Dench as the 19th-century queen.
Director James Toback brings together Sienna Miller and Alec Baldwin in independent drama "The Private Life of a Modern Woman", and Spanish power couple Javier Bardem and Penelope Cruz appear in "Loving Pablo" by Fernando Leon de Aranoa.
A Lifetime Achievement Award will be picked up by Jane Fonda and Robert Redford, who will also present their new film "Our Souls at Night", directed by Ritesh Batra.
"American Beauty" star Annette Bening heads the jury for the festival, which runs from Aug. 30 until Sept. 9.
(Writing by Isla Binnie; Editing by Robin Pomeroy)