Endometriosis is a disease that affects between 6 and 10% of women of childbearing age. It is defined by the presence of endometrial tissue outside the uterine cavity, most often in the ovaries or the peritoneal cavity. The standard treatment for endometriomas is laparoscopic intraperitoneal cystectomy. This treatment has been shown to be associated with a lower rate of recurrence of painful symptoms than simple cyst drainage, and with higher pregnancy rates. Nevertheless, cystectomy can lead to a reduction in ovarian reserve due to the removal of adjacent healthy ovarian tissue, particularly when there is no cleavage plane between the ovary and the endometrioma. Other methods have been developed to manage endometriomas while preserving the ovarian reserve. Endometrioma sclerotherapy is one of the most promising techniques for reducing the risk of recurrence while preserving the ovarian reserve. This technique involves injecting a sclerosing agent into the cystic cavity, which has been drained beforehand, in order to create an abrasion of the cystic epithelium, resulting in inflammation and fibrosis that can lead to the permanent destruction of the cyst. The aim of the study is to conduct a single-centre randomised controlled non-inferiority trial comparing sclerotherapy and intraperitoneal cystectomy for the treatment of endometriomas. The main hypothesis of the study is that sclerotherapy is not inferior to cystectomy in terms of reducing painful symptoms one year after the operation and that it is superior to cystectomy on one or more of the following criteria: preservation of ovarian reserve, operative complications, post-operative pain, patient acceptability/satisfaction. The number of patients to be included will be 64, calculated to demonstrate non-inferiority between sclerotherapy and cystectomy for the primary endpoint.