Top Hollywood talent and auteur directors will be vying for the Golden Lion at the world's oldest film festival which, after a period in the doldrums, is again seen as a launch pad for the industry's award season after premiering Academy winners in its last three editions.
Space drama "Gravity", comedy "Birdman" and last year's clergy sex abuse film "Spotlight" secured Oscars after premiering in Venice and those wins have helped attract talent to this year's festival, said artistic director Alberto Barbera.
"The second element is that this year there is a lot of good stuff around," he told Reuters as the red carpet was laid out in preparation for the star-filled line-up.
The rich selection of US and international movies include Damien Chazelle's "La La Land", the festival's opener, starring Stone and Gosling in a musical comedy-drama about a jazz pianist who falls in love with an aspiring actress in Los Angeles.
"'La La Land' is something that everyone is talking about," said Variety film critic Jay Weissberg. "As much as maybe people don't even want to admit that they like musicals, everybody kind of likes a musical."
Others include fashion designer Tom Ford's thriller "Nocturnal Animals" and Denis Villeneuve's science fiction drama "Arrival", both featuring Amy Adams, and Gibson's "Hacksaw Ridge".
Also hotly anticipated are the first two episodes of Paolo Sorrentino's mini TV series "The Young Pope", featuring Law as a conservative, cigarette-smoking American pontiff Pius XIII, which will screen in an out-of-competition section.
"They think that he's going to be more liberal but it turns out he's much more conservative, so in a way it's the opposite of Pope Francis ... it's a brilliant concept," Weissberg said.
Concrete slabs were positioned at entrances to control vehicle traffic, and security officials were screening arrivals at the festival venue on the eve of the event which runs until Sep 10.
"After all the terrorist attacks in Europe the security is one of the main issues," Barbera said, but added the measures would be sufficiently discreet to not disturb the festival.
A new, cube-shaped theatre will open during the event, bearing witness to some of the work done since Barbera returned at the helm of the festival in 2012 and made restoring the site to its former glory a priority.
The festival organisers have cancelled the beachside gala dinner scheduled for Wednesday in respect of the nearly 300 victims of the earthquake that hit central Italy last week.
"We are here for a festival which is a cultural event, we don't want to give up of course on the event but we want to give a concrete sign of our solidarity to the victims," Barbera said.