The London Scottish was a reserve infantry regiment then a company of the British Army. In its final incarnation it was A (The London Scottish) Company, the London Regiment until, on 1 May 2022, soldiers in the company transferred to foot guards regiments and the company became G (Messines) Company, Scots Guards, 1st Battalion London Guards.

The regiment was founded on the formation of the Volunteer Force in 1859. Originally as part of the Volunteer Force sponsored by the Highland Society of London and the Caledonian Society of London, a group of individual Scots raised the London Scottish Rifle Volunteers under the command of Lt Col Lord Elcho, later The Earl of Wemyss and March. The regiment became the 7th (London Scottish) Middlesex Volunteer Rifle Corps and then, in 1908, the 14th (County of London) Battalion, London Regiment (London Scottish).

The 1/14th Battalion was mobilized on the outbreak of war, departing for France on 15 September 1914. On 31 October 1914 the battalion encountered German forces at Messines in Belgium, the first territorial unit to do so – a memorial stands on the site. The 2/14th Battalion embarked for France in June 1916 but was then transferred to Salonika and Palestine.

In 1937, on the break-up of the London Regiment, the unit was re-named The London Scottish, The Gordon Highlanders.

The London Scottish raised three battalions during the Second World War, two of which served overseas. Both of the overseas battalions served with the Middle Eastern Forces in Sicily and Italy. The battalions were:

The peacetime battalion of the regiment, served as infantry within the 168th (London) Infantry Brigade (alongside the 1st London Irish Rifles and 10th Royal Berkshire Regiment), part of the 56th (London) Infantry Division (nicknamed "The Black Cats"), playing a significant part in the Italian Campaign, fighting in the Allied invasion of Sicily, fighting at Monte Cassino, Battle of Anzio, Gothic Line (afterwards transferred to 167th (London) Infantry Brigade) and Operation Grapeshot, the final offensive in Italy in 1945.

Raised as a 'duplicate' of the 1st Battalion, with a core of officers and senior NCOs from that battalion. The battalion initially served in the 141st (London) Infantry Brigade, 47th (London) Infantry Division.

When the duplicate battalion was formed in April 1939, the regiment had enough recruits to form a third battalion; permission was granted provided it was formed as an anti-aircraft (AA) regiment of the Royal Artillery. It was designated 97th (The London Scottish) Heavy Anti-Aircraft Regiment, RA and formed with HQ and two batteries (298 and 299) at Westminster. It served in 1st AA Division (the old 47th (2nd London) Division) defending London during the Battle of Britain and the Blitz. In March 1943 it left for North Africa where it joined British Eighth Army, and served with it in the Allied invasion of Sicily and Italian Campaign. With the depletion of the Luftwaffe and the reduced requirement for AA defences, it was converted in November 1944 into 97th (London Scottish) Garrison Regiment, RA, later designated 610 Infantry Regiment, RA. When the TA was reconstituted in 1947, 610 Regiment was reformed as 497th (London) Heavy Anti-Aircraft Regiment, RA at Hammersmith, later renamed 497th (Hammersmith) Heavy Anti-Aircraft Regiment, RA, without any London Scottish connection.