The Mercedes-Benz 190 SL (W121) is a two-door luxury roadster produced by Mercedes-Benz between May 1955 and February 1963. Internally referred to as W121 (BII or B2), it was first shown in prototype at the 1954 New York Auto Show, and was available with an optional removable hardtop.

The 190 SL presented an attractive, more affordable alternative to the exclusive Mercedes-Benz 300 SL, sharing its basic styling, engineering, detailing, and fully independent suspension. Both cars had double wishbones in front and swing axles at the rear. Instead of the 300 SL's expensive purpose-built W198 tubular spaceframe, the 190 SL's R121 structure used a shortened unitary floorpan modified from the W121 base saloon.

The 190 SL was powered by a new, slightly oversquare 105 PS (77 kW; 104 hp) Type M121 BII 1.9 L straight-four SOHC engine. Based on the 300 SL's straight six, it had an unchanged 85 mm bore and 4.3 mm reduced 83.6 mm stroke, was fitted with twin-choke dual Solex carburetors, and produced gross 120 hp (89 kW; 122 PS). In detuned form, it was later used in the W120 180 and W121 190 models.

The car was available either as a soft-top convertible (initially priced at DM 16,500/US$3,998[4]) or with removable hardtop (DM 17,650/$4,295). A small third-passenger transverse seat was optional. During its first years the 190 SL was available as a sports-racing model with small perspex windscreen and spartan one-piece leather covered bucket seats and aluminium doors. In 1959, the hardtop's rear window was enlarged.

In 1956, a few six-cylinder prototypes were built for testing. A 190SL with a unique engine, using the 300SL block, squeezed into the engine bay with a one-off mix of Benz-bin parts was entered in the 1956 Alpine Rally, but the costs of production would be prohibitive. Two other prototypes, fitted with fuel injected M180 220SE engines were baptised the W127 / 220SL. In June 1956, Rudi Uhlenhaut and Karl Kling lapped the Nürburgring Nordschleife circuit in the two W127s 25 seconds faster than a regular 190SL. On 12 April 1957, MB's board decided to build the W127, six-cylinder 220SL alongside the 190SL, but production challenges postponed manufacturing until it was overtaken by the 230SL 'Pagoda'.

Both the 190 SL and the 300 SL were replaced by the Mercedes-Benz 230SL in 1963.