Over eight decades, the institutions designed to govern a postwar world have remained largely frozen while the world they govern has transformed beyond recognition. The Global South, now accounting for more than forty percent of world economic output, is no longer content to receive rules written by others—it is pressing, through reform and parallel institution-building, to become a co-author of the international order. This is not a revolt against multilateralism but a demand that multilateralism finally mean what it promises: governance by and for all.