The gluteal sulcus (also known as the gluteal fold, fold of the buttock or horizontal gluteal crease) is an area of the body of humans and great apes, described by a horizontal crease formed by the inferior aspect of the buttocks and the posterior upper thigh. The gluteal sulcus is formed by the posterior horizontal skin crease of the hip joint and overlying fat, and is not formed by the lower border of gluteus maximus, which crosses the fold obliquely.