A rear-view mirror is a mirror

Mirror

A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...

 in automobile

Automobile

An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

s and other vehicles, designed to allow the driver to see rearward through the vehicle's backlight (rear windscreen).

In cars, the rear-view mirror is usually affixed to the top of the windscreen on a swivel

Swivel

A swivel is a connection that allows the connected object, such as a gun or chair, to rotate horizontally and/or vertically. A common design for a swivel is a cylindrical rod that can turn freely within a support structure. The rod is usually prevented from slipping out by a nut, washer or...

 mount allowing it to be freely rotated. In the past, some cars had the rear-view mirror mounted on top of the dashboard

Dashboard

A dashboard is a control panel placed in front of the driver of an automobile, housing instrumentation and controls for operation of the vehicle....

. Rear-view mirrors are designed to break away to minimize injury to occupants who may be thrown against it in a collision

Car accident

A traffic collision, also known as a traffic accident, motor vehicle collision, motor vehicle accident, car accident, automobile accident, Road Traffic Collision or car crash, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other stationary obstruction,...

.

For motorcycles and bicycles, the rear-view mirrors are usually mounted to the handlebars, and there are usually two of them, so they are variously referred to as "rear-view mirrors", "side-view mirrors", "side mirrors", or simply "mirrors".
The rear-view mirror's earliest known use and mention is by Dorothy Levitt

Dorothy Levitt

Dorothy Elizabeth Levitt, was a motorina and sporting motoriste of the early 20th century. On 4 July 1903 she was reported as the first woman ever to compete in a motor race...

 in her 1906 book The Woman and the Car which noted that women should "carry a little hand-mirror in a convenient place when driving" so they may "hold the mirror aloft from time to time in order to see behind while driving in traffic", thereby inventing the rear view mirror before it was introduced by manufacturers in 1914.
The earliest known rear-view mirror mounted on a motor vehicle appeared in Ray Harroun

Ray Harroun

Ray Harroun was an American racecar driver, born in Spartansburg, Pennsylvania.-Early driving:As noted in the Columbia Car webpages, Harroun participated in the original setting of the record from Chicago to New York in 1903, and the re-taking of that record in 1904...

's Marmon racecar at the inaugural Indianapolis 500

Indianapolis 500

The Indianapolis 500-Mile Race, also known as the Indianapolis 500, the 500 Miles at Indianapolis, the Indy 500 or The 500, is an American automobile race, held annually, typically on the last weekend in May at the Indianapolis Motor Speedway in Speedway, Indiana...

 race in 1911.