Long-term nuclear waste warning messages are communication attempts intended to deter human intrusion at nuclear waste repositories in the far future, within or above the order of magnitude of 10,000 years. Nuclear semiotics is an interdisciplinary field of research, first established by the American Human Interference Task Force in 1981.

A 1993 report from Sandia National Laboratories recommended that such messages be constructed at several levels of complexity. They suggested that the sites should include foreboding physical features which would immediately convey to future visitors that the site was both man-made and dangerous, as well as providing pictographic information attempting to convey some details of the danger, and written explanations for those able to read it.