1931年「九一八事變」爆發後，隔年滿洲國宣告成立。國際聯盟（League of Nations）與世界各國普遍不承認滿洲國為新興獨立國家，英國也堅持東北地區為中華民國領土，主張英國國民在東北的通商口岸和滿鐵附屬地仍享有治外法權；滿洲國剛建國時，根基未穩，因而新京當局承認英國享有上述權利。但事實上，英國的治外法權在法理及實踐層面，時常遭遇滿洲國當局、關東軍、關東廳（後改組為關東局）及日本駐滿洲國使領館的挑戰。隨著滿洲國逐漸掌控當地秩序，無論在滿洲國本土或滿鐵附屬地，英國領事對涉及英國人刑事案件的司法管轄權和對英國企業的保護都不斷被削弱。尤其是1936-1937年，關東軍為打擊滿鐵、實現權力一元化，廢除了日本在滿洲國的治外法權，此舉「殃及池魚」，連帶在法理上也否定了英美等國的治外法權。1941年，日本與英、美正式決裂，英國在滿洲國的治外法權實際上徹底終結。本文以關涉英國國民及企業治外法權的重要案件為線索，檢視自滿洲國建國至「珍珠港事變」爆發期間英國在滿洲國治外法權的廢除歷程，探討1930年代英日兩帝國在東亞如何實現權力轉移，日本及滿洲國當局又如何在東北地區擺脫華盛頓體系及條約體系的約束而重塑秩序，以及日本以何種方式維繫「日滿一體」的特殊關係。

The Mukden Incident occurred in 1931, and Manchukuo was established in 1932. The major powers and the League of Nations did not give de jure or de facto recognition to Manchukuo. As Britain still regarded Manchuria as under the jurisdiction of the Republic of China, British subjects still enjoyed extraterritoriality in the treaty ports and the South Manchuria Railway Zone in Manchuria. As a new-born government, the Hsinking Authorities could not afford to irritate Britain so they also recognized Britain’s extraterritoriality in Manchuria. However, whether in theory or practice, Britain’s extraterritoriality was increasingly challenged by the Hsinking Authorities, the Kwantung Army, the Kwantung Government (later the Kwantung Bureau), and the Japanese Embassy and Consulates in Manchukuo. Britain’s jurisdiction over its subjects’ criminal cases and its corporations’ protection was being shattered. From 1936-1937, the Kwantung Army abolished Japan’s extraterritoriality in Manchuria in order to decrease the power of the South Manchuria Railway Co. Ltd, leading to the abolition of de jure British extraterritoriality in Manchukuo as a chain reaction. In 1941, Japan declared war on Britain and the U.S., therefore, de facto Britain’s extraterritoriality was utterly abolished. Through an exploration of British and Japanese diplomatic documents of the period, the study examines the process of abolishing Britain’s extraterritoriality, investigates the power shift between Britain and Japan in East Asia, as well as how the Japanese Empire maintained and consolidated its relations with Manchukuo through its informal empire. Finally, this paper sheds lights on the British retreat from East Asia from the establishment of Manchukuo to the Japanese surprise attack on Pearl Harbor.