The Lotus Mark X was an aluminium-bodied sports racing car manufactured by Lotus Engineering Ltd.

The Mark X, of which only 6 or 7 were made, was essentially identical to the Mark VIII but made use of the larger 2.0-litre Bristol engine. The Mark VIII, Mark IX and Mark X were transitional forms although they represent the first full bodied aerodynamic Lotus sports cars, they made use of the De Dion tube as a rear suspension locator, and also inboard rear brakes. The more successful Lotus Eleven, of which 270 were manufactured between 1956 and 1958 was the direct descendant of these earlier cars. The earlier cars are today considered rare and highly valued collectible automobiles, even museum pieces, but can still be seen raced in vintage events.