Ball lightning has been extensively reported, usually in association with thunderstorms, by chance observers who constitute perhaps five percent of the adult U.S. population. These sightings have been documented by polling such observers, and what is known about the characteristics of ball lightning is the result of information which emerged from these polls. This data base is useful because it reveals a phenomenon with very interesting implications for fusion energy, and it provides important constraints on theoretical models of ball lightning. Unfortunately ball lightning itself has not been accessible to scientific analysis, because it has not been possible to reproduce it in the laboratory under controlled conditions. Natural ball lightning has been observed to last longer than 90 seconds, and to have diameters from one centimeter to more than one meter. The energy density of a few lightning balls has been observed to be higher than 20,000 joules per cubic centimeter, well above the limit of chemical energy storage of, for example, TNT at 2000 joules per cubic centimeter. Such observations suggest a plasma-related phenomenon with significant magnetic energy storage and excellent confinement. Ball lightning should provide a novel paradigm in fusion research, as well as being of great theoretical and practical interest to the plasma research community.