The Eleven was designed by Colin Chapman and fitted with a sleek body designed by aerodynamicist Frank Costin. Its standard version, dubbed Le Mans, was fitted with a 1100 cc (67ci Coventry Climax engine mounted in the front of a tubular space frame and featured a De Dion rear axle and 9.5 in (240 mm) Girling disc brakes. Fully loaded, the car weighed only about 1,000 lb (450 kg). Versions for a 1100 cc (67ci) Climax engine (Club) and a 1172 cc (72ci)[3] Ford engine (Sport) were also produced; both featured a live rear axle and drum brakes. Some versions of the Le Mans were fitted with a closed body with gullwing doors to meet GT specifications.

Lotus Eleven at Donington ParkDespite the wide variety of engines installed, the car was primarily designed to compete in the 1100 cc class where it was one of the most successful cars during the mid- to late-1950s. Some cars were later fitted with 1500cc (92ci) Coventry Climax engines in order to compete in the 1500cc class. In 1956, An Eleven, modified by Costin with a bubble canopy over the cockpit, was driven by Stirling Moss to a class world record of 143 mph (230 km/h) for a lap at Monza. Several class victories at Le Mans and Sebring followed, and the Eleven became Lotus' most successful race car design.

 In 1957, the Eleven underwent a major design change, including a new front suspension and improvements to the drivetrain. Although officially called Eleven Series 2, these late models are sometimes informally referred to as Lotus 13s, since they were produced between the 12 and 14 models and the 13 designation was not used by Lotus.

A road legal car was tested by the British magazine The Motor in 1957 and had a top speed of 125 mph (201 km/h) and could accelerate from 0-60 mph (97 km/h) in 10.0 seconds. A fuel consumption of 39.0 miles per imperial gallon (7.24 L/100 km/32.5 mpg-US) was recorded. The test car cost £2,501 including taxes of £811