This paper analyses the structuring role that the Milky Way performs in the worldview of the Mocoví of the Southern Chaco (Argentina, South America). Since 1998, we have been working on a research project that involves anthropological fieldwork in order to understand Mocoví ethnoastronomy, its changes and variations, and its relationships with other regional indigenous systems of astronomy. Through an analysis of historical chronicles, early ethnographic literature and data from our own fieldwork, the present paper shows how the different interpretations the Mocoví give to the Milky Way relate to one another.