Many indigenous peoples span state borders, yet little research has analyzed how indigenous cross-border nations are actually constructed and how contemporary state borders are implicated in that process. This dissertation begins to address that puzzle by focusing on how the Maya-Mam, an indigenous people divided by the Guatemala-Mexico border, are actively imagining and constructing nationhood across state borders. Although state borders socially, culturally, and politically divide the pueblo Mam, the Mam are engaged in denaturalizing such borders in their efforts to seek collective rights as a cross-border nation. This dissertation highlights how leaders of Mam councils, Mam organizations, and also individuals in their everyday lives who self-identify as Mam are denaturalizing state borders through three processes. First, I address how the Mam define their symbolic boundaries of collective identification in relation to spatial boundaries of different scales. Second, I analyze how cross-border experiences (i.e., social interactions among Mam councils and individuals from opposite sides of the border) are shaping Mam collective identification as a cross-border nation. And third, I address how the Mam are counter-mapping their ancestral territory by producing geographic and political representations that challenge state maps and the nation state framework. I suggest that these three processes have an interwoven character (i.e., they feed into each other), which I refer to as imagining cross-border belonging. I conceptualize imagining cross-border belonging as an active reconstruction of space (both physical and symbolic) across state borders. I argue that imagining cross-border belonging constitutes a symbolic struggle with material, and even spatial, consequences linked to the collective rights of cross-border nations.