The Jaguar XJ (X350) is a full-size four-door luxury saloon car manufactured and marketed worldwide by Jaguar Cars for model years 2003–2009 as the third generation of the Jaguar XJ saloon, carrying the internal designation X350 and the internal designation X358 following its 2007 intermediate facelift. Both the X350 and X358 were available with a six-speed automatic transmission, a range of petrol and diesel engines, numerous trim levels, and short wheelbase (2003–2009) or long wheelbase (2005–2009) car body configurations. Extended-length models were the longest vehicles Jaguar had manufactured.

Jaguar is the sports car and luxury vehicle brand of Jaguar Land Rover, a British multinational car manufacturer with its headquarters in Whitley, Coventry, England. Jaguar Cars was the company that was responsible for the production of Jaguar cars until its operations were fully merged with those of Land Rover to form Jaguar Land Rover on 1 January 2013.