The UK bought Phantom versions based on the U.S. Navy's F-4J for use by both the Royal Air Force and the Royal Navy’s Fleet Air Arm. The UK was the only country outside the USA to operate the Phantoms at sea, launching them from HMS Ark Royal aircraft carrier.

The main differences between the F-4J and FG.1 were the use of the British Rolls-Royce Spey engines and inclusion of British-made avionics. The Royal Navy and RAF versions were given the designation F-4K and F-4M respectively, and entered service with the British military aircraft designations Phantom FG.1 (fighter / ground attack) and Phantom FGR.2 (fighter / ground attack / reconnaissance).

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Initially, the Phantom FGR.2 was used in the ground attack and reconnaissance role, primarily with RAF Germany, while 43 Squadron was formed in the air defence role using the FG.1s that had been intended for the Fleet Air Arm for use aboard HMS Eagle.

The superiority of the Phantom over the ageing English Electric Lightning in terms of both range and weapons load, combined with the successful introduction of the SEPECAT Jaguar, meant that, during the mid-70s, most of the ground attack Phantoms in Germany were redeployed to the UK to replace air defence Lightning squadrons. A second RAF squadron, 111 Squadron, was formed with the FG.1 in 1979 after 892 NAS was disbanded.