A chocolate cyst, also known as an endometrioma or endometriotic cyst, is a type of cyst that forms in the ovaries due to endometriosis. Endometriosis is a condition where the tissue similar to the lining of the uterus grows outside the uterus, leading to inflammation, scarring, and sometimes the formation of cysts. These cysts can vary in size and may cause symptoms such as pelvic pain, especially during menstruation, pain during intercourse, and fertility problems.

The term "chocolate cyst" comes from the dark, reddish-brown fluid inside the cyst, which resembles chocolate syrup. This fluid is made up of menstrual blood that has accumulated over time within the cyst.

Treatment for chocolate cysts may involve medication to manage symptoms such as pain or hormonal treatments to suppress menstruation and slow the growth of endometrial tissue. In some cases, surgery may be necessary to remove the cyst, especially if it is large, causing severe symptoms, or affecting fertility.