The intergluteal cleft, also known by a number of synonyms, including natal cleft, anus slice, butt crack, and cluneal cleft, is the groove between the buttocks that runs from just below the sacrum to the perineum, so named because it forms the visible border between the external rounded protrusions of the gluteus maximus muscles. Other names are the anal cleft, crena analis, arena interglutealis, “cleftal horizon”, and rima ani. Colloquially the intergluteal cleft is known as bum crack (UK) or butt crack (US). The intergluteal cleft is located superior to the anus.
