The Jaguar XJ is a series of mid-size/full-size luxury cars produced by British automobile manufacturer Jaguar Cars from 1968 to 2019. It was produced across five basic platform generations with various updated derivatives of each. From 1970, it was Jaguar's flagship four-door model. The original model was the last Jaguar saloon to have been designed under the leadership of Sir William Lyons, the company's founder, and the model has been featured in countless media and high-profile appearances.

Jaguar's independent rear suspension (IRS) unit has been a common component of a number of Jaguar production cars since 1961, passing through two major changes of configuration up to 2006 and last used in the Jaguar XK8 and Aston Martin DB7. This article concentrates on the first generation Jaguar IRS, which firmly established the marque's reputation for suspension sophistication, combining as it did smooth ride with excellent roadholding and low levels of noise, vibration, and harshness (NVH). The two generations overlap in time due to their being used in both full size and sports models that were updated at different times.