Abstract: Described herein are exemplary embodiments of patient positioning systems for supporting and positioning a patient in an inclined position during medical treatment, such as in the Reverse Trendelenburg position. Some embodiments comprise a flexible, air-impermeable shell having a torso portion configured to support the patient's torso and secure the positioner to the support surface, an intermediate portion integrally coupled to an inferior end of the torso portion, and a suprapubic portion integrally coupled to an inferior end of the intermediate portion opposite the torso portion and configured to extend along the patient's perineal-pubic region when the shell is evacuated of air. When evacuated of air, the positioner is configured to hold the patient in an inclined position on an inclined support surface with the patient's head above the patient's hips such that the intermediate and/or suprapubic portions physically block the patient from sliding feet-first down the inclined support surface.