The sacrospinous ligament is a thin ligament attached to the ischial spine (a bone prominence in the lower pelvis)  and the lateral (side) regions of the sacrum (at the bottom of the spine) and coccyx, or tailbone. A ligament is a strong, fibrous connective tissue that usually connects bone to bone.

The sacrospinous ligament borders the sacrotuberous ligament and shares fiber space with this ligament. The sacrospinous and sacrotuberous ligaments work together to limit the upward tilt of the sacrum, called nutation. The sacrospinous and sacrotuberous ligaments are most notably stressed when a person leans forward or stands up.

This pair of ligaments helps to transition the greater and lesser sciatic notches (indentations) into the greater and lesser sciatic foramens (openings). This anatomical transition occurs based on the boundary caused by upper and lower placement of the ligaments in proximity with the notches.

Several blood vessels, arteries and nerves surround this ligament, including the pudendal vessels, the inferior gluteal artery, the pudendal nerve, and the sciatic nerve.

When ligaments in the pelvis and the surrounding tissue become damaged or are absent in females, this may cause prolapse, or falling, of the vagina or uterus. An operation called sacrospinous suspension may be used as treatment. This surgery involves stitching the sacrospinous ligament to the cervix or vaginal vault in order to restore support.