An image display system includes: an image projection unit that projects and displays an image on a display target for a moving body; a posture angle calculation unit that calculates a posture angle for the moving body on the basis of chronological data for acceleration detection values for the acceleration of the moving body in a prescribed time period; and a display control unit that controls the display position at which the image is projected and displayed on the display target, in accordance with the posture angle calculated by the posture angle calculation unit. The acceleration detection values include bi-directional components. The posture angle calculation unit excludes acceleration detection values from the chronological data used when calculating the posture angle, said acceleration detection values being included in an exclusion time period which has a ratio for the bidirectional components, in the prescribed time period, that is outside a prescribed range.