Within the enduring effort to rethink geography from multiple viewpoints and new conceptual categories, critical geographers have recently sought to “decentralize geopolitics” (An, Sharp, and Shaw 2021) by proposing alternative analyses that can tackle the Eurocentric stance that has largely defined the field. This paper contributes to this decentralizing effort by bringing into light, historically, an anti-imperial discourse that took the form of a proper geographical invention. Specifically, the paper analyzes the thought of the Mexican intellectual José Vasconcelos – who acted as Secretary of Public Education in the aftermath of the Revolution (1921-1924) – and argues that Vasconcelos' discourse represents a "subaltern” intervention against the imperial presuppositions of the newborn discipline of geopolitics. The paper contends that Vasconcelos' thought constitutes a conscious attempt, although clearly imbued with "postcolonial" tensions and contradictions, to challenge the "scientific" basis of the emerging geopolitical discourse at that time. By analyzing Vasconcelos' geographical and geo-social imagination through his recuperation of the myth of Atlantis and the idea of Cosmic Race, the paper illuminates an early operation of "subaltern geopolitics" (Sharp 2011) that aimed to contrast the new wave of Western imperialism which, intensively nurtured by socio-environmentalist narratives, strongly defined the turn of twentieth the century.