The W126 series premiered in late 1979 as 1980 model (and 1981 in USA). The W126 line introduced a host of new safety features, and ushered in the next phase of Mercedes-Benz styling. The W126 S-Class was also the first luxury car to win the prestigious Car of the Year award from Australia’s Wheels Magazine, which it did in 1981. The W126 line lasted from 1979 through 1991, a production run of over twelve years. Total sales of the W126 S-Class sedans reached 818,036 units, with an additional 74,060 coupes sold. These sales figures make the W126 the most successful S-Class line in Mercedes-Benz history.

In 1981, the W126 re-introduced the airbag to the world, as an additional measure of occupant protection. Other safety innovations on the W126 included passenger side airbags (in 1986), seat-belt pretensioners, and traction control. In the cabin, additional courtesy and reading lamps, along with heated seats and a more advanced climate control system, added to the luxurious interior environment. A four-speed automatic transmission was standard.

Although the top of range Mercedes-Benz 450SEL 6.9 of the previous generation was not directly replaced, the W126 carried forward the hydropneumatic suspension of the 6.9 as an option on the 500SEL. A new cruise control system was offered as well. Abandoning the roadster based coupes, the W126 introduced a two door variant, the SEC coupé. The longevity of the W126 S-Class model cycle was aided by a mid-cycle update in 1986, an upgrade which previously was not done in S-Class generations. During the update of the W126 model S-Class, a facelift was performed and engine upgrades occurred.