Overcoming limitations of previous fluorescent light-up RNA aptamers for super-resolution imaging, we present RhoBAST, an aptamer that binds a fluorogenic rhodamine dye with fast association and dissociation kinetics. Its intermittent fluorescence emission enables single-molecule localization microscopy with a resolution not limited by photobleaching. We use RhoBAST to image subcellular structures of RNA in live and fixed cells with about 10-nm localization precision and a high signal-to-noise ratio.