The coccyx (or tailbone, coccyges, latin: os coccygis) is the final bony segment of the vertebral column that consists of three to five rudimentary vertebrae. The coccyx is located below the sacrum and attaches to it by the sacrococcygeal symphysis.

The coccyx of an adult usually presents as a single bone formed by three, four or five fused vertebrae. However, it is not a rule, as the coccyx may consist of two to five separate bony segments.

There is a coccygeal cornu (horn) featured on each side of the coccyx, which is a paired process projecting upwards formed by the superior articular process of the coccyx.