Longitudinal vaginal septum is a rare mullerian anomaly and its association with pelvic organ prolapse (POP) is unusual. A case of longitudinal vaginal septum with stage IV POP in a 35-year-old multiparous woman is being reported. Examination revealed an incomplete longitudinal vaginal septum (9 x 6 x 2 cm) with stage IV POP. Vaginal hysterectomy with repair and reconstruction was done along with excision of the longitudinal vaginal septum which was technically challenging due to proximity to rectum. This is the only case report of stage IV pelvic organ prolapse associated with a thick longitudinal vaginal septum in a multiparous woman without any obstetric complications. Surgery required increased caution per operatively while dissecting the septum from the vaginal wall and the adjacent organs.