Force 136 was a far eastern branch of the British World War II intelligence organisation, the Special Operations Executive (SOE). Originally set up in 1941 as the India Mission with the cover name of GSI(k), it absorbed what was left of SOE's Oriental Mission in April 1942. The man in overall charge for the duration of its existence was Colin Mackenzie.

The organisation was established to encourage and supply indigenous resistance movements of British ruled India in enemy-occupied territory, and occasionally mount clandestine sabotage operations. Force 136 operated in the regions of the South-East Asian Theatre of World War II which were occupied by Japan from 1941 to 1945: Burma, Malaya, Sumatra, Siam, and French Indochina (FIC).

Although the top command of Force 136 were British officers and civilians, most of those it trained and employed as agents were indigenous to the regions in which they operated. Burmese, Indians and Chinese were trained as agents for missions in Burma, for example. British and other European officers and NCOs went behind the lines to train resistance movements. Former colonial officials and men who had worked in these countries for various companies knew the local languages, the peoples and the land and so became invaluable to SOE. Most famous amongst these officers are Freddie Spencer Chapman in Malaya and Hugh Seagrim in Burma.

SOE was formed in 1940, by the merger of existing Departments of the War Office and the Ministry of Economic Warfare. Its purpose was to incite, organise and supply indigenous resistance forces in enemy-occupied territory. Initially, the enemies were Nazi Germany and Italy, but from late 1940, it became clear that a conflict with Japan was also inevitable.

Two missions were sent to set up (and assume political control of) the SOE in the Far East. The first was led by a former businessman, Valentine Killery of Imperial Chemical Industries (ICI), who set up his HQ in Singapore. A scratch resistance organisation was set up in Malaya, but Singapore was captured on 15 February 1942, soon after Japan entered the war.

A second mission was set up in British India by another former British colonial businessman, Colin Mackenzie of J. and P. Coats, a clothing manufacturer. Mackenzie's India Mission originally operated from the city of Meerut. Its location was governed by the fear that the Germans might overrun the Middle East and the Caucasus, in which case resistance movements would be established in Afghanistan, Persia and Iraq. When this threat was removed late in 1942 after the battles of Stalingrad and El Alamein, the focus was switched to South East Asia.

The India Mission's first cover name was GS I(k), which made it appear to be a record-keeping branch of GHQ India. The name, Force 136 was adopted in March 1944. From December 1944, the organisation's headquarters moved to Kandy in Ceylon and co-operated closely with South East Asia Command which was also located there.

In 1946, Force 136 was wound up, along with the rest of SOE.