Abstract: A new and improved portable ergonomic cushion for relieving pressure on the coccyx (tailbone) and on the ischial tuberosities, for promoting correct positioning of the sacroiliac joint and for supporting the lower back of the user is described. The portable ergonomic cushion includes a narrow ridge back support allowing the cushion to be used with numerous styles of chairs and seats, and a lumbar support cushion that is removably attached to the back support. The portable ergonomic cushion may also make use of inflatable cushions for increasing the flexibility of the sitting cushion by allowing users to adjust the cushions to their desired support by varying the amount the cushions are inflated. The portable ergonomic cushion is also foldable into a compact non-use position for easy transportation and storage, and futher does not require the use of straps for retaining the cushion while in use.