The 42-year-old actress has served as something of a muse for the Danish director, having also starred in his films Antichrist and Melancholia. Gainsbourg plays the lead character Joe, a self-diagnosed nymphomaniac, in Von Trier's films of the same name. The movie was split into two volumes, released March 6 and 20 in the U.S.
The film raised eyebrows with its highly sexual content, and Gainsbourg acknowledged that work with Von Trier is certainly never dull.
"I take every film with Lars as a different experience and the way it happens is always a surprise," the actress said in an interview with IndieWire. "He's very unpredictable so I'm just very happy I was able to do those three films and for him to take me to really different places each time."
Gainsbourg said her work with the provocative director has decreased her bashfulness, but hasn't necessarily led to more confidence. "I have no shyness... [but] there's still a lot of fear that I won't be able to do what he wants."
"I didn't go into [Nymphomaniac] fearless. I was very scared of a lot of things that I'd have to go through. I'd never read a script like that before... With all those digressions, the material was so rich that it was very exciting."
The film tells Joe's story as she relates her entire sexual history to the character Seligman, played by Stellan Skarsgård. Stacy Martin plays a young Joe. Gainsbourg was clear that porn doubles performed all of the risqué sex scenes and that there was never a possibility of her performing the acts herself.
"It was obvious I wasn't going to do it," the actress stated. "That was part of the deal and there was no trying to be manipulated in any way... [Von Trier] was very respectful of all the actors and all the porn actors, too. It was all happening in good spirit."
Gainsbourg pointed out that the films incorporate a sense of humor among the more controversial scenes. She said that Nymphomaniac has a "very weird sense of humor, very disturbing... I was disturbed, embarrassed and a little humiliated but I wanted to go there."
"I think it's a film about a woman portraying herself, with all her suffering and all her faults," the actress added. "She tries to portray herself as a terrible, bad human being and by the end, I think she understands more of who she is."