The XK120 was launched as an open two-seater or (USA) roadster at the 1948 London Motor Show as a testbed and car show for the new Jaguar XK engine.

The display car was the first prototype, chassis number 660001.

It looked almost identical to the production cars except that the direct external pillars of the windshield would be curved in the production version.

The sports car caused a sensation, which persuaded Jaguar founder and president William Lyons to put it into production.

Beginning in 1948, the first 242 cars used open 2-seater bodies with wooden frames and aluminum panels.

Production switched to the heavier 1cwt or 51kg in the early 1950s.

The "120" in the name referred to the top speed of 193 km / h of the aluminum car (faster with the windshield). removed), which made it the fastest production car in the world at the time of its launch.

In 1949, the first production car, chassis number 670003, was delivered to Clark Gable.

The XK120 was finally available in three versions or body styles, first as a 2-seater opener described in the US market as a roadster (OTS), as a fixed coupe (FHC) from 1951 and finally as a dropup coupe (DHC). from 1953, all two seats and are available with Left (LHD) or Right Hand Drive (RHD).

A smaller engine version with a 2-liter 2-cylinder engine, designated the XK100, intended for the UK market, was canceled before production.

On May 30, 1949, on the empty Ostend-Jabbeke highway in Belgium, an XK120 prototype, programmed by officers from the Royal Automobile Club of Belgium, achieved an average of 132.6 mph running in opposite directions with the windshield replaced by just one. small aero screen and a cataloged alternative top gear ratio, and 135 mph with a passenger side tonneau cover in place.

In 1952, a fixed coupe took several world records for speed and distance when averaging 100 mph for a week.

The XK120s were also highly successful in racing and rallying.