The 300 SL's racing ancestor, the W 194, was developed by Daimler-Benz in 1951 using a 3-litre inline-six M 186 engine shared with the 300 "Adenauer" saloon. Although the engine produced less power than competing Ferraris and Jaguars, the W 194's low weight and aerodynamic efficiency made it competitive in endurance racing.
The idea to produce a road car from the racing concept came from Max Hoffman, Mercedes-Benz's United States importer, who proposed it at a 1953 directors' meeting in Stuttgart. New general director Fritz Konecke agreed to Hoffman's order for 1,000 cars. The 300 SL was introduced not at a European show but at the February 1954 New York International Auto Show, reflecting its primary target market. Production began at the Sindelfingen plant in August 1954.
The abbreviation "SL" stood for "Super Leicht" (super-light), a designation confirmed by a chance archival discovery and updated on the company website in 2017, replacing the earlier "Sport Leicht" wording used for decades.
The 300 SL was built around a tubular spaceframe of chrome-molybdenum steel, designed by Rudolf Uhlenhaut. Thin straight tubes were assembled as triangles, and the finished frame weighed just 82 kilograms. The spaceframe's high lateral tubes between the wheels ran level with the driver's elbow, making conventional door hinges impossible — the only solution was the upward-opening gullwing door that became the car's defining visual element.
The M 198 engine was a water-cooled 3.0-litre overhead cam straight-six derived from the M 186, tilted 50 degrees toward the driver's side to allow a lower bonnet line. The key performance advance was replacing the triple Solex carburetors with Bosch mechanical direct fuel injection, raising output from 175 hp (130 kW) to 240 hp (179 kW) at 6,100 rpm. With the lowest available final-drive ratio of 1:3.25, the 300 SL reached a top speed of 263 km/h (163 mph), making it the world's fastest production car of its era.
The front suspension used unequal-length double wishbones, coil springs, and telescopic dampers. The rear used a low-pivot swing axle with coil springs. Drum brakes were standard; disc brakes replaced them in March 1961.
The body was predominantly steel, with the bonnet, boot lid, dashboard, sill, and door skins in aluminium. An all-aluminium body was available at extra cost, of which only 29 were produced.
The W 194 racer preceding the road car established the template in 1952. At that year's 24 Hours of Le Mans, Kling, Hermann Lang, and Fritz Riess took a 1-2-3 finish after the leading Ferrari broke down. The same year at the Nürburgring, the team ran a roadster configuration with the passenger side covered. At the Carrera Panamericana in Mexico, Kling and Klenk finished first, with Lang and Erwin Grupp second.
In production-car racing, the 300 SL dominated the Sports Car Club of America Class D championship from 1955 to 1957. Werner Engel won the 1955 European Rally Championship in a 300 SL. John Fitch won his class at the 1955 Mille Miglia in a production coupé, while Stirling Moss won the overall title in the related 300 SLR racing car. Liege-Rome-Liege rally wins followed in 1955 with Olivier Gendebien and 1956 with Willy Mairesse.
Sales of the gullwing coupé began declining in mid-1956, prompting Mercedes to develop a convertible version aimed at the California market. Shown at the Geneva Motor Show in March 1957, the roadster required a redesigned spaceframe with lowered sills to permit conventional door hinges, which also improved access significantly over the awkward high-sill coupé.
The roadster's rear suspension was improved: the swing axle's pivot point was lowered 87 mm below the differential centreline, dramatically improving handling and reducing the snap-oversteer tendency that characterised the coupé at the limit. Engine power was set at 240 hp (179 kW). Weight increased by 35 kg to 1,330 kg due to the frame revisions. Production of 1,858 roadsters ran until February 1963, making it the last Mercedes-Benz car built on a separate frame.
The 300 SL spawned the smaller 190 SL roadster in 1955 and established the SL lineage that continues through multiple generations. The gullwing coupé's design was directly honoured by the SLS AMG, which debuted in 2009 with similar gullwing doors, produced through 2014. The 300 SL remains among the most recognised and sought-after classic cars in the world, with significant examples commanding auction prices reflecting its historical and cultural status.