A smart key is an electronic access and authorization system that is available either as standard equipment or an option in several car designs. It was developed by Siemens in 1995 and introduced by Mercedes-Benz under the name "Keyless-Go" in 1998 on the W220 S-Class, after the design patent was filed by Daimler-Benz on May 17, 1997.

The Mercedes-Benz W220 was a range of flagship sedans which, as the fourth generation Mercedes-Benz S-Class, replaced the W140 S-Class after model year 1998 — with long and short wheelbase versions, performance and luxury options; available four-wheel drive; and a range of diesel as well as gas/petrol V6, V8, and V12 engines. Compared to its predecessor, the W220 had somewhat smaller exterior dimensions but offered greater interior volume, particularly in the long-wheelbase versions, and slightly less cargo volume.