Fatigue is complex, representing simultaneously a physiological, psychological and social phenomenon. The sociological approach attempts to understand the experience of fatigue and its characterization at diverse periods and in various social contexts. After giving a sociological history of different forms of fatigue through the ages (acedia, melancholy, neurasthenia, chronic fatigue syndrome, etc.), this article proposes a social epidemiology of fatigue in the current period. Objectification of working and living conditions allows us to illustrate social inequalities in fatigue and exhaustion, but seems to contradict dominant social representations of fatigue today. It invites a critical discussion of contemporary theories of fatigue (such those of Alain Ehrenberg or Byung-Chul Han), which consider that fatigue is a condition of modern man, overwhelmed by his freedom. More modestly, analysis of the fatigue presented here rests on the capacity to be able to find a good balance between too much investment in work or life (which is exhausting) and not enough investment (which leads to boredom and lack of self-fulfillment). This balance depends on fragile and specific social norms in different professional or social circles and cannot be defined a priori.