Endometriosis is a common gynecological disorder that is defined by the presence of endometrial tissue outside the uterine cavity. This disease often results in extensive morbidity, including chronic pelvic pain and infertility. The pathogenesis of endometriosis is likely multifactorial, and extensive investigation has explored the role of genetics, environmental factors, and the immune system in predisposing patients to developing endometriosis. A series of recent publications have described the identification of endometrial stem/progenitor cells. Such cells have long been speculated to function in the cyclic regeneration of the endometrium during the menstrual cycle and in the pathogenesis of several gynecological disorders. This narrative review will (i) examine the evidence for endometrial stem cells, (ii) examine their potential role in the pathogenesis of endometriosis, and (iii) identify important unanswered questions with suggestions for future investigation.