The Jaguar XK series comprises three closely related sports cars — the XK120 (1948–1954), XK140 (1954–1957) and XK150 (1957–1961) — all built around the 3.4-litre (later 3.8-litre) twin-cam XK inline-six that powered Jaguar through the 1950s and into the E-Type era. Each generation was offered as an Open Two Seater (OTS) Roadster, a Fixed Head Coupe (FHC) and a Drophead Coupe (DHC).
The XK120 launched at the 1948 London Motor Show and took its name from a factory 120 mph run at Jabbeke, Belgium. The first 242 Roadsters were built with hand-formed aluminium bodies over ash frames (Wikipedia, citing the model's production history); of those, 184 were left-hand drive per the RM Sotheby's Miami 2025 catalogue. Volume steel-body production began in early 1950. The XK140 (1954–1957) introduced revised bumpers, a larger grille, rack-and-pinion steering and — with the engine moved forward — a meaningfully more usable cabin, including 2+2 seating on the FHC and DHC. The XK150 (1957–1961) followed with wider bodywork, a one-piece curved windscreen, a raised wing line and, from launch, standard four-wheel disc brakes; its 3.4S and 3.8S 'S' specifications, running triple SU carburettors, are the acknowledged performance flagships of the entire XK range.
Jaguar's XK-era production figures come from three parallel published sources — the Jaguar Heritage Trust (JHT) archive, XKData.com's chassis-sequence registry, and Graham Robson's A–Z of British Cars 1945–1980 (Herridge, 2006). Small discrepancies of a few units across these sources are consistent between generations and are shown below rather than smoothed over.
The XK series introduced the twin-cam XK engine, established Jaguar's post-war sports car reputation and directly seeded the C-Type, D-Type and E-Type that followed. It is the founding pre-E-Type Jaguar collector market.