A keyless entry system is an electronic lock that controls access to a building or vehicle without using a traditional mechanical key. The term keyless entry system used to mean a lock controlled by a keypad located at the door, that requires pressing a predetermined numeric code for entry.

The term remote keyless system (RKS), or more commonly just as keyless entry, refers to a lock that uses an electronic remote control as a key which is activated by a handheld device or automatically by proximity.

Widely used in automobiles, an RKS performs the functions of a standard car key without physical contact. When within a few yards of the car, pressing a button on the remote can lock or unlock the doors, and may perform other functions. A remote keyless system can include both a remote keyless entry system (RKE), which unlocks the doors, and a remote keyless ignition system (RKI), which starts the engine.

Remote keyless systems first began appearing on the French made Renault Fuego in 1982, and as an option on several American Motors vehicles in 1983, including the Renault Alliance. The feature gained its first widespread availability in the U.S. on several General Motors vehicles in 1989.