Quadratus is Latin for square and quadratus muscle may refer to:
Depressor labii inferioris muscle, also known as musculus quadratus labii inferioris Levator labii superioris muscle, also known as musculus quadratus labii superioris Pronator quadratus, a square shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand Quadratus femoris muscle, a flat, quadrilateral skeletal muscle. Located on the posterior side of the hip joint Quadratus lumborum muscle, a muscle of the posterior abdominal wall Quadratus plantae muscle, a muscle in the foot