78th Searchlight Regiment (78th S/L Rgt), was an air defence unit of Britain's Royal Artillery during World War II.

The regiment was created as part of the rapid expansion of anti-aircraft (AA) defences during the Battle of Britain.

[2] By the time 78th S/L Rgt joined, The Blitz was in full swing, with frequent night air raids on the industrial cities.

The cluster system was an attempt to improve the chances of picking up enemy bombers and keeping them illuminated for engagement by AA guns or night fighters.

Then on 24 July 498 and 500 S/L Btys became independent while Regimental HQ and the remaining battery, 551, were reduced to a cadre; they were disbanded on 8 September.

Of the two independent batteries, 500 began the process of disbandment on 15 December, completing it by 7 January 1944, while 498 transferred C and D Troops to 310 Independent HAA Bty on 28 February 1944 and the rest of the battery began disbanding, completing the process by 20 March.