The Theory of Everything Oscar winner spent three years learning from members of the trans community to prepare for his role as Lili Elbe, known as one of the first recipients of sex reassignment surgery.
"People were so kind and generous with their experience, but also so open," Redmayne, 33, tells Out magazine in their upcoming cover story. "Virtually all of the trans men and women I met would say, 'Ask me anything.' They know that need for cisgender people to be educated."
He adds, "I felt like, I'm being given this extraordinary experience of being able to play this woman, but with that comes this responsibility of not only educating myself but hopefully using that to educate [an audience]. Gosh, it's delicate. And complicated."
Born in 1882, Elbe was an early icon for the transgender community. The movie, which is based on David Ebershoff's 2000 novel of the same name, is the story of her life, love, art and courage to come out as trans at the turn of the century.
Eddie Redmayne as Lili Elbe in THE DANISH GIRL. Directed by Tom Hooper, the film is currently in production. pic.twitter.com/Ue9cVuE1rR— Working Title (@Working_Title) February 27, 2015
Her story, first chronicled in the 1933 book Man into Woman: The First Sex Change, would go on to become a major inspiration for another trailblazer in the trans community: Matrix co-director Lana Wachowski.
As part of his trans education, Redmayne spent time with the director, and spoke to her about the book's influence on her journey. "I did start talking to Lana about Lili and she told me how important the book, Man into Woman, was to her. And also the art, specifically of [her husband] Gerda. She very kindly continued my education, pointed me to literature, and where I should be headed."
After reading Ebershoff's script, Redmayne says, "I found it profoundly moving. I knew nothing about it going in. It felt like it was a piece about authenticity and love and the courage it takes to be yourself."
Learning about Elbe also helped the actor examine his own masculinity. "I suppose it depends on what you think of as masculine and feminine," he tells the magazine. "I was musical, and I was into theater and arts, but I was also into sports, so I had quite a broad spectrum. I can also totally see that other people see a femininity in me."
Ultimately, the actor says he learned that gender identity is "fluid" and "needn't be labeled." He adds, "My greatest ignorance when I started was that gender and sexuality were related. And that's one of the key things I want to hammer home to the world: You can be gay or straight, trans man or woman, and those two things are not necessarily aligned."
Redmayne, who hopes the film will be educational as well as entertaining, also gave credit to Caitlyn Jenner for her role in fueling the current conversation regarding the trans community.
"I absolutely salute her courage," the actor said, noting that, "Hers is a very specific story, and it's one that shouldn't stand for everybody's. But it is amazing what she's gone through and how she's done it."
Ensuring that trans people have a voice today is a "civil rights movement," Redmayne says.
The Danish Girl hits theaters Nov. 27.