The actress had been resting up due to a 'rough patch' with her illness.
Girls' creator Lena Dunham was hospitalized this weekend due to a ruptured ovarian cyst, a common side effect of endometriosis.
Cindi Berger, Dunham's spokesperson, confirmed the hospitalization to ET in a statement. "Lena Dunham has been very public with her personal bouts with endometriosis. This morning she suffered from an ovarian cyst rupture and has been taken to the hospital. Lena will be undergoing surgery at an undisclosed hospital. We thank you for your understanding and hope that Lena's privacy will be respected."
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Dunham's hospitalization comes just three weeks after the actress announced she wouldn't be participating in the press tour for the sixth and final season of Girls, her HBO series.
At that time, the 29-year-old explained that she was "going through a rough patch" with her endometriosis and that she needed a break.
Dunham and pals addressed the illness in a recent issue of her newsletter Lenny devoted to endometriosis.
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In the newsletter's introduction it is explained that endometriosis is "when the cells that line the uterus (endometrial cells) end up in other parts of the body," which can result in painful cysts, scar tissue, and blocked fallopian tubes, among other side effects.
Dunham has been an outspoken advocate on women's issues, and recently spoke up to support Kesha in her battle with music producer Dr. Luke. Find out more in the video below.