Hathaway arrived by boat with director Jonathan Demme to present her latest film, "Rachel Getting Married," which is appearing in competition at the festival.
In the film she plays Kym, a turbulent woman who brings havoc to a family gathering as they celebrate the marriage of her sister Rachel.
"I never saw her in any of those ways, I mean, I know technically she is, but I just thought she's a girl struggling to live an honest life. And she is honest, fiercely honest, painfully honest, impolitely honest, and that was so much fun to play. It was so much fun to be the combustible element in a scene, very often times, I've never played a character like this before, very often I'm reacting to someone else, it was kind of fun to be the centre of the turmoil," she said.
Hathaway told reporters that she had no sister, but did have two brothers, so knew all about the joys and frustrations family events could bring:
"I'm not sure if I have ever fought with anyone quite the way Kym fights with people but...And I actually, my two brothers are my best friends so I don't really fight with them all that much. I think I'm a little bit more passive than Kym."
Hathaway and the rest of the cast will walk the red carpet later on Wednesday.
The Golden Lion will be presented by the Venice jury for the best film in competition on Sept. 6, 2008.