The gluteus maximus is the main extensor muscle of the hip. It is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips. Its thick fleshy mass, in a quadrilateral shape, forms the prominence of the buttocks. The other gluteal muscles are the medius and minimus, and sometimes informally these are collectively referred to as the "glutes".
