The Lotus 18 was Colin Chapman's first mid-engined Formula I car. The previous Lotus 12 and 16 were front engined and, although they had a Chapman-designed space frame chassis, were not successful. The rival mid-engined Coopers had a traction advantage that gave them the World Championship in 1959 and 1960.

The space frame Lotus18 was designed to be an uncomplicated race car with minimal frontal area and low center of gravity. The car was to be a multipurpose Formula I, Formula II, or Formula Jr. depending what size engine was used. The front suspension had double unequal-length wishbones. A lower wishbone, twin trailing arms attached to the chassis, and the wheel half-shafts formed the rear suspension. Later, the rear suspension was modified to double wishbones, thus relieving the drive half-shafts of any wheel locating function. The half-shaft couplings were changed to rubber doughnuts (rotoflex) since the half-shafts now effectively had to change length as the suspension flexed. The rear disk brakes were moved outboard for better cooling. The photo below shows Stirling Moss trying out the 18.

The Formula I debut for the Lotus 18 was in the 1960 Argentine Grand Prix with Innes Ireland driving. The car was second fastest in qualifying, outfitted with a Coventry-Climax FPF 2.5-litre, 237-hp engine. Ireland led the race for a number of laps. However, due to mechanical problems that developed during the race, Ireland finished in sixth place.

In early March 1960 at Oulton Park Innes Ireland scored Team Lotus' first Formula II win, bettering the existing lap record by an impressive 5.2 seconds. Sixteen days later at Goodwood, Ireland won the Formula I and II races, thoroughly trouncing Stirling Moss in his Rob Walker Cooper in both races. At Moss' insistence, a Lotus 18 was ordered for him, delivery coming in time for the Monaco Grand Prix. Moss broke the existing track record in qualifying and, inspite of an unscheduled pit stop, won the race.

Ireland winning F-1 race at Goodwood, 1960

Moss also won the German and U.S. Grands Prix that year. In 1961 Moss took victory away from three heavily favored Ferraris at Monaco and also won the German Grand Prix in the Lotus 18. The first Team Lotus Grand Prix victory that counted for World Championship points was garnered when Innes Ireland won the U.S. Grand Prix at Watkins Glen in 1961.

After the Lotus 18 started to win regularly, Chapman was inundated with orders and eventually around 150 cars were built and delivered. The 18 established Lotus as a force to be reckoned with in Formula I. Chapman, starting with this mid-engine, space frame design, went on to build the cars that set the standard for Formula I.