This paper argues that the collective action in Asia by its regional organizations has historically suffered from a "capability–legitimacy gap": a disjuncture between the capability (in terms of material resources) of major Asian powers to lead regional cooperation on the one hand and their political legitimacy and will as regional leaders on the other. Successful collective action requires leadership with both capability (as suggested by rationalist theories) and legitimacy (as suggested by constructivist approaches). A central point of the paper is that the putative or aspiring leaders of Asian regionalism throughout the post-war period never had both.