This special epidemiological report presents the epidemiological characteristics of Legionnaires' disease cases reported in 2015 among residents of Auvergne-Rhône-Alpes and compares them with those observed over the past five years in the region and with national averages. Given the west-to-east gradient in the disease’s incidence, Auvergne-Rhône-Alpes is among the regions most affected by Legionnaires’ disease. In 2015, while the disease’s incidence rate showed a clear downward trend, approaching the national average incidence rate, this trend remains to be confirmed. This decline was observed in nearly all departments of the broader region. The characteristics of those affected—in terms of gender, age, exposure factors, and case fatality rate—have changed little and are close to national averages.