Ericson fluctuations constitute one of the most characteristic features of quantum chaotic scattering in the regime of strongly overlapping resonances such as a compound nucleus. These fluctuations were predicted in 1960 by Torleif Ericson in two seminal articles, further developed in 1963, based on the same statistical assumptions as those used by E. Wigner, C. E. Porter and R. G. Thomas to describe generic properties of resonances in long-lived compound nuclear systems. In the present case the fluctuations occur in the "continuum" regime for which a large number of such resonances overlap coherently, owing to the short lifetime of the compound nucleus. At the time it was believed that this would lead to a structure-less behavior. Ericson realized that the opposite was the case with strong, random fluctuations.