Gate-all-around integrated circuit structures having depopulated channel structures, and methods of fabricating gate-all-around integrated circuit structures having depopulated channel structures using a bottom-up oxidation approach, are described. For example, an integrated circuit structure includes a vertical arrangement of nanowires above a substrate. The vertical arrangement of nanowires has one or more active nanowires above one or more oxidized nanowires. A gate stack is over the vertical arrangement of nanowires and around the one or more oxidized nanowires.