The Jaguar XJ13 is a prototype racing car that was developed by Jaguar Engineering Director William Heynes to compete at Le Mans in the mid 1960s. It never raced, and only one was produced.

The design structure of a mid-engined prototype was first mooted in 1960 by William Heynes, but it was not until 1965 that construction began, with the first car running by March 1966. The aluminium body exterior was designed by Malcolm Sayer, the aerodynamicist responsible for aerodynamic air flow work on the Jaguar C-type and D-type. He used his Bristol Aeroplane Company background to build it using techniques borrowed from the aircraft industry. The task of building the car was entrusted by Heynes to Engineer Derick White, Ted Brookes, Mike Kimberley, and Bob Blake in the Browns Lane experimental department's competition shop

Blake described by his contemporaries as An Artist in Metal. William Heynes recognised as early as 1964 that a car such as the XJ13 needed an experienced race driver to help develop it. Jack Brabham was approached in this regard,but the challenge was eventually taken up by ex-Jaguar Apprentice David Hobbs,who was recruited as the XJ13's main test driver. In 1969, Hobbs was included in a FIA list of 27 drivers who were rated the best in the world. Hobbs achieved an unofficial UK closed lap record with the XJ13 which stood for 32 years. For the XJ13's final test at full racing speed, Hobbs was joined at Silverstone by another racing driver (and ex-Jaguar apprentice)