United Kingdom Commando Force (UKCF), previously called 3 Commando Brigade (3 Cdo Bde), is the UK's special operations-capable commando formation of the Royal Marines. It is composed of Royal Marine Commandos and commando qualified personnel from the Royal Navy, British Army and Royal Air Force.

The brigade was formed 1 September 1943 at Dorchester with personnel from 102 RM Brigade, during the Second World War, with a mixture of Army Commando and Royal Marine Commando units, and was deployed to the South-East Asian Theatre of World War II to conduct operations against the invading forces of Imperial Japan, such as the Burma Campaign. After the Second World War, the Army Commandos were disbanded and the brigade became a Royal Marine formation. Recently, United Kingdom Commando Force has again become a mixed formation with the addition of commando qualified soldiers from the Royal Artillery and Royal Engineers to provide support for the Royal Marine Commandos. Since the end of the Second World War, it has been involved in a number of engagements such as the Suez Crisis, Falklands War, Gulf War and the War in Afghanistan.

Between September and November 1943, in Scotland, 102nd Brigade, Royal Marines Division, was detached from the division, to form the independent 3rd Special Service Brigade – a joint British Army-Royal Marines formation. The founding commander was Brigadier Wilfrid Nonweiler and it was composed of the following units:

Nos. 1 and 5 Commandos had already earned battle honours as units in, respectively, the North African and Madagascar campaigns. Because "Commando", at the time, implied a company/battalion-sized unit, the name "Special Service" was instead used for British commando brigades. (However, the term "Commando Brigade" was often used informally, because "Special Service" was unpopular and had a superficial similarity to the name of the notorious German Schutzstaffel (SS).) The brigade was later officially renamed 3rd Commando Brigade.

On 10 November 1943, elements of the brigade embarked at Gourock, bound for India. It was intended that the brigade would be used in operations against Japanese forces in the South-East Asia theatre, such as the Burma campaign. However, the limited shipping capacity available at the time meant that the relocation was prolonged and the components of the brigade were not reunited until late 1944. Lt Col. Peter Young was transferred from the Normandy campaign to become second-in-command of 3rd Commando Brigade. Young succeeded Nonweiler as commander of the brigade.

During January 1945, the brigade was involved in the campaign to recapture Arakan, including the battles of Myebon peninsula and Kangaw. The brigade was then withdrawn to India to prepare for Operation Zipper, a proposed amphibious operation to recapture the Malayan peninsula. The atomic bombs against Japan precipitated an earlier surrender of Japan than expected. The 3rd Commando Brigade moved to secure Hong Kong – a British crown colony that was under Japanese occupation in 1941–45. During 1946, British Army personnel and units within the 3rd Commando Brigade were demobilised or transferred elsewhere and it became a Royal Marine formation.

3 Commando Brigade's most high-profile operation after the war was the Suez Crisis, when it took part in the amphibious assault against Egyptian targets. During Operation Musketeer, units of the brigade made a helicopter-borne assault.

1971 saw the withdrawal of British forces from the Far East and Persian Gulf. The brigade returned to the UK with other British units. It moved to Stonehouse Barracks in Plymouth, where it remains to this day.