Dunham filmed a video with co-stars Allison Williams, Jemima Kirke and Zosia Mamet, asking society to break an unwritten code of silence around sexual assault and create a culture that encourages women to come forward.
The video calls on everyone to “support, listen and take action.”
“I dedicate this to the brave survivor in the Stanford case who has given so much to change the conversation,” Dunham wrote on Twitter.
Nearly a week ago, the unnamed victim faced her attacker, Brock Turner, in Santa Clara County Supreme Court, reading aloud a poignant and graphic letter recounting the January 2015 incident at Stanford University and the pain she has endured.
"The next thing I remember I was in a gurney in a hallway. I had dried blood and bandages on the backs of my hands and elbow," the victim stated in the letter.
She detailed her state of disbelief upon first learning what had happened to her saying, "I said, this can't be me."
She blasted her attacker, who partly blamed his actions on the drinking culture in college: "Show men how to respect women, not how to drink less.”
The letter was published online by Buzzfeed and other outlets and went viral, garnering over 11 million views and creating an outcry across the Internet.
“This letter the defendant...it was raw, it was a universal pain that she describes to eloquently and that makes it different," ABC News senior legal correspondent Sunny Hostin said. "This is a watershed moment when it comes to victims of sexual assault…she has now made it okay to come forward.”
Along with the “Girls” cast, actress Brie Larson, who won an Oscar for portraying a kidnapped woman held captive for years by her rapist in the film "Room," expressed her outcry on Twitter.
Sexual assault is "the most under-reported crime" in the country, according to the U.S. Department of Justice, and 90 percent of sexual assault incidents that occur on college campuses are never reported.
Turner, 20, was convicted of sexual assault and sentenced to six months in jail and three years of probation last week. Turner plans to appeal his conviction.