Piezo1 is the stretch-activated Ca²⁺ channel in red blood cells that mediates homeostatic volume control. Here we study the organization of Piezo1 in red blood cells using a combination of super-resolution microscopy techniques and electron microscopy. Piezo1 adopts a nonuniform distribution on the red blood cell surface, with a bias towards the biconcave "dimple". Trajectories of diffusing Piezo1 molecules, which exhibit confined Brownian diffusion on short timescales and hopping on long timescales, also reflect a bias towards the dimple. This bias can be explained by "curvature coupling" between the intrinsic curvature of the Piezo dome and the curvature of the red blood cell membrane. Piezo1 does not form clusters with itself, nor does it co-localize with F-actin, Spectrin or the Gardos channel. Thus, Piezo1 exhibits the properties of a force-through-membrane sensor of curvature and lateral tension in the red blood cell.