Lieutenant-General Sir Derek Boileau Lang KCB DSO MC (7 October 1913 − 7 April 2001) was a senior British Army officer who served in the Second World War and was later General officer commanding-in-Chief (GOC-in-C) of Scottish Command.

In February 1938 he was sent to Scotland where he became adjutant to the regiment's 4th Battalion, a Territorial Army unit serving as part of the 51st (Highland) Division, then commanded by Major General Victor Fortune.

[2] Still adjutant upon the outbreak of the Second World War in September 1939, Lang was sent to France, along with the rest of the 51st Division, in January 1940, where it formed part of the British Expeditionary Force (BEF).

He returned to the United Kingdom and, eventually, went on to be Commanding officer (CO) of the 5th Battalion, Queen's Own Cameron Highlanders from July 1944.

Both the original brigade and division had been captured, as had Lang himself, in France in June 1940 but had been reformed that August by redesignating the 9th (Highland) Infantry Division and, after having served in North Africa and Sicily, were now fighting in Normandy in the aftermath of the D-Day landings.