Chronic pelvic pain is defined as pain situated below the umbilicus, for at least 6 months, that causes functional disability or requires treatment. Although chronic pelvic pain is a common presentation to gynecology clinics, only 20% of these cases are attributed to gynecologic causes including endometriosis. In this chapter, we discuss gynecologic and non-gynecologic causes of chronic pelvic pain and how to differentiate through history, examination, and work-up.