When French demographer Alfred Sauvy coined the term “Third World” in 1952, it sketched the outlines of a vision only beginning to perceive that the impoverished, decolonizing areas of the world did not fit into the bipolar scheme of the Cold War. But this vision did not i nclude Latin America, whose decolonization had unfolded more than a century earlier. As the post-war waves of that process brought dozens of new nation-states into the atlas, its coincidence with the Cold War drew a second set of lines, splitting the earth into three “worlds”—the Third of these eventually comprising most of the Global South. However, the waves of decolonization after 1945 did not produce the full membership of this imagined community. When later married to shared interests in nonalignment, economic development, and race-conscious activism, the result expanded the meaning and membership of “Third World” to include the western hemisphere below the Rio Grande. This essay explores the evolution of the term “Third World” from its original incarnation, denoting the decolonizing European empires, to its fullest iteration at the inclusion of Latin America. The Cold War battle for “hearts and minds”—a contest not just between East and West but between North and South—sparked and shaped this evolution. It created the intellectual and geopolitical space for what would come to be called the Third World. Over time, that space was repossessed and redefined by “native” actors themselves, including those in Latin America. By 1970, a confluence of currents brought Latin America into agreement with the new nation-states of Asia, Africa, and the Middle East, whose leaders found enough common ground in the “Third World” to conjoin all their regions within it—an imagined community which itself sought to transcend the Cold War.