The Greater East Asia Co-Prosperity Sphere (Japanese: 大東亞共榮圏 / Dai Tōa Kyōeiken) is a proposed military, economic, and cultural union of East Asian nations led by the Empire of Japan. The concept emerged following the Weltkrieg, when it became clear to Japanese military and political leaders that Japan's resources, such as they were, would be unable to support a prolonged war of attrition in isolation. Having turned away from the Entente following the war's conclusion, and given the rise of the United States, Russia, and Germany as regional rivals, these ideas have since played into existing narratives surrounding Japan's perceived struggle against the western world, in which Japan is often held to be the heroic vanguard at the head of a broader Pan-Asian cause.
The idea's nature, and the manner in which it is articulated, varies widely across the Japanese political spectrum. Some academics and politicians see the Sphere as a manifestation of Pan-Asian ideals, while others, pragmatists and militarists in particular, see it instead as a vehicle to strengthen Japan's position in the region. Most see neither of these ideas as exclusive, and view them as fundamentally intertwined.