The Mercedes W123 is a range of executive cars produced by the German manufacturer Mercedes-Benz between January 1976 and January 1986.

The W123 models outperformed its predecessor, the Mercedes-Benz W114 models, as the most successful Mercedes, selling 2.7 million cars before being replaced by the Mercedes-Benz W124 after 1985. The additional range of smaller Mercedes-Benz models W201 was introduced in 1982.

As usual, the model names were related to engine sizes, engine type and chassis type:

C for Coupe
T for Tourismus und Transport (estate / station wagon)
The long wheelbase model was simply called "Lang" (long)
D for Diesel
Turbo for Turbodiesel
And for Einspritzung (fuel injection)
As for the chassis codes, the W123 is the regular sedan, the S123 the property, the C123 the coupe, the V123 the Lang and the F123 for the bare chassis, used for ambulances and other conversions.

Mercedes-Benz introduced the four-door versions of the W123 on January 29, 1976. Although there were some technical similarities to its predecessors, the new models were greater in wheelbase and external dimensions. The style has also been updated, although stylistic links with the W114 / W115 have been maintained. Initially, all models, except the 280 / 280E, had rounded square headlights of different sizes and the last large rectangular units. When facelifted, these units have become standard across the range. All W115 engines were transported, with the 5-liter 3-cylinder diesel model being renamed "240D 3.0" to "300D" (as it has been called before in North American markets). The only new engine was the 2,525 inline-six (type M123) of 250, a single overhead camshaft design that took the place that the M130 had within the W114 series.



Coupe (C123)
In the spring of 1976, a coupe version was introduced with a shorter wheelbase than in the saloon (2,710 mm versus 2,795 mm for the saloon). This W123C / CE was available as a 230C (later 230CE) and as a 280C / CE in most markets; in North America there were additional versions of 300 CDs with 3-liter diesel engines naturally aspirated and later turbocharged. In North America, buyers preferred diesel engines for luxury cars, while CAFE legislation meant that Mercedes-Benz North America had to reduce its average corporate fuel economy. This led to the introduction of some diesel models sold only in the United States.
It is a tribute to the car's instant popularity - and possibly the caution built into production schedules - that, nine months after its introduction, a black market had developed in Germany.