Endometriosis is a chronic condition that may cause pelvic pain, ovarian cysts, infertility, and recurrent symptoms. This prospective observational cohort study will enroll women aged 18 to 45 years with endometriosis and age- and body mass index-matched healthy women. Participants will receive routine clinical care, and the study will not assign medications or procedures. Baseline clinical information will be collected, and participants will be followed for 24 months, every 3 months during the first year and every 6 months thereafter. The study will assess cyst recurrence, pain recurrence, pregnancy and live birth outcomes, and other long-term clinical outcomes. It will also evaluate associations between disease characteristics, rASRM stage, routine medical treatment, and subsequent clinical and reproductive outcomes, and will support the establishment of an endometriosis clinical research database.