This entry introduces several scholarly literatures on radio with the aim of amplifying possible responses to the question: How might we define radio as “wireless sound”? The entry begins by describing the material and institutional apparatus by which radio coheres around the globe, and subsequently canvasses media studies, philosophy, postcolonial theory, and art writing and art practices through which radio and wireless sound have become the objects of analysis, philosophical speculation, and aesthetic experimentation. It concludes by contextualizing the insights of these diverse literatures by reference to ethnographic fieldwork on radio and music production in Aboriginal Northern Australia. Ethnographic work within this field of Indigenous cultural production frames radio’s power through the ways it stages intimacy as the foundation of collective self-abstraction, foregrounding forms of metapragmatic discourse and media ideology by which radio’s technologies feed back into Aboriginal social life.