| 5th Bn, King's Own Yorkshire Light Infantry 53rd (KOYLI) LAA Regiment, RA 57th (KOYLI) LAA Regiment, RA | |
|---|---|
 KOYLI cap badge, featuring a light infantry horn and White Rose of York | |
| Active | 1 April 1908 – 10 March 1955 |
| Country |  United Kingdom |
| Branch |  Territorial Army |
| Role | Infantry Air defence |
| Size | 1-3 Infantry battalions 2 Artillery regiments |
| Part of | 148th (3rd West Riding) Brigade 187th (2/3rd West Riding) Brigade Eighth Army 4th Indian Division Anti-Aircraft Command |
| Garrison/HQ | Doncaster |
| Engagements | World War I: |
| Commanders | |
| Notable commanders | Lt-Col Oliver Watson, VC, DSO Maj-Gen William Revell-Smith Brig Percy Calvert-Jones |
The 5th Battalion, King's Own Yorkshire Light Infantry (5th Bn KOYLI), was a unit of Britain's Territorial Force formed in 1908 from Volunteer units originally raised in the West Riding of Yorkshire in 1860. It served in some of the bitterest fighting on the Western Front during World War I, leading the attack at the tank battle of Cambrai and defending Bucquoy in March 1918. In the late 1930s, the battalion was converted to air defence in which role it served during World War II in the Battle of France and the Dunkirk evacuation, in North Africa including the Second Battle of El Alamein, and in the Allied invasions of Sicily and Italy, including service in the rebellion in Greece. Postwar, its successor units served in Anti-Aircraft Command until 1955.