The advances in 5G mobile networks are expected to enable immersive interconnected mobile multimedia systems. As humans are the final judges of the quality of immersive multimedia, it is essential to engage a suitable ground truth in the design of such systems. Databases annotated with results from subjective tests constitute such ground truth given as opinion scores, head movements, eye tracking data, psychophysiological data, and other data related to the viewers' behavior. On this basis, perception-based quality assessment of algorithms, systems, and services can be performed, and objective perceptual quality models can be developed. In this paper, a comprehensive survey of publicly available annotated 360-degree image and video databases is provided. The survey may guide the selection of ground truth on 360-degree images and videos to support quality assessment and modeling research. Further, the survey reveals the need for establishing new annotated databases that address the full range of subjective aspects of immersive multimedia. © 2019 IEEE.