The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends.

This ligament runs from the sacrum (the lower transverse sacral tubercles, the inferior margins sacrum and the upper coccyx) to the tuberosity of the ischium. The membranous falciform process of the sacrotuberous ligament was found to be absent in 13% of cadavers. When present, it extends toward the ischioanal fossa, traveling along the ischial ramus and fusing with the obturator fascia. The sacrotuberous ligament contains the coccygeal branch of the inferior gluteal artery.

The lower border of the ligament was found to be directly continuous with the tendon of origin of the long head of the biceps femoris in approximately 50% of subjects. The biceps femoris could, therefore, act to stabilise the sacroiliac joint via the sacrotuberous ligament.

If the pudendal nerve becomes entrapped between this ligament and the sacrospinous ligament causing perineal pain, the sacrotuberous ligament is surgically severed to relieve the pain.