The Lotus Mark IX (1955) was an aluminium-bodied sports racing car manufactured by Lotus Engineering Ltd.. About thirty of the Mark IX sports racing cars were made. It was closely related to the Lotus model Mark VIII (1954), of which only about seven cars were made. These cars were largely based on the innovative space frame of the Lotus Mark VI (1952). The highly aerodynamic bodies were designed by Frank Costin and constructed by Williams & Pritchard Limited.