The Mercedes-Benz 300 SL (chassis code W 198) is a two-seat sports car that was produced by Mercedes-Benz from 1954 to 1957 as a gullwinged coupé and from 1957 to 1963 as a roadster. The 300 SL traces its origins to the company's 1952 racing car, the W194, and was equipped with a mechanical direct fuel-injection system that increased the power output of its three-liter overhead camshaft straight-six engine.

The 300 SL was capable of reaching 260 km/h (162 mph), earning it a reputation as a sports car racing champion and making it the fastest production car of its time. The car's iconic gullwing doors and innovative lightweight tubular-frame construction were groundbreaking.

The designation "SL" is an abbreviation of the German term super-leicht, meaning "super-light", a reference to the car's racing-bred lightweight construction. The 300 SL was introduced to the American market at the suggestion of Max Hoffman, Mercedes-Benz's United States importer at the time, who recognized the potential demand for a high-performance sports car among American buyers. The Mercedes-Benz 300 SL remains a highly sought-after classic car and is celebrated for its performance, design, and technological advancements.

The 300 SL traces its origin to an endurance racer, the Mercedes-Benz W194, developed by Daimler-Benz in 1951. It used the 3-liter inline-6 M186 engine, shared by the company flagship 300 "Adenauer" saloon (W186) and the two-seat 300 S grand tourer (W188).

Although W194's 175 hp (130 kW) engine produced less power than competing cars by Ferrari and Jaguar, its low weight and low aerodynamic drag made the W194 fast enough to be competitive in endurance races.

Mercedes-Benz developed a new version for the 1953 racing season by replacing the M186's carburetors with mechanical direct fuel-injection, and shifting to 16-inch wheels; the gearbox was installed on its rear axle. Its body was made of Elektron, a magnesium alloy, which reduced its weight by 85 kilograms (187 pounds). Mercedes-Benz decided not to race this alloy car, choosing instead to begin participating in Formula One in 1954. Later versions revised the body to lower air resistance, and did not continue the transmission arrangement.

The idea of Mercedes producing a toned-down Grand Prix car targeted to affluent performance enthusiasts in the booming post-war American market was suggested by the company's U.S. importer, Max Hoffman, at a 1953 directors' meeting in Stuttgart. Mercedes' new general director, Fritz Konecke, agreed to Hoffman's order for 1,000 cars to guarantee the success of the production run; the 300 SL was introduced at the February 1954 New York International Auto Show instead of the Frankfurt or Geneva shows, where company models usually debuted. In addition, the production of a smaller roadster, the Mercedes-Benz 190 SL, was announced after Hoffman placed an initial order for 1,000 to support their production. Mercedes received a positive visitor response to both cars in New York, and production began at the Sindelfingen plant in August of that year.

The price for the 300 SL coupé in Germany was DM 29,000, and $6,820 in the US.^{[as of?]} The roadster was DM 32,500 in Germany, and $10,950 in the US – 10 percent more expensive than the coupé in Europe, and over 70 percent more in the US.^{[as of?]}