Fatigue is a complex issue linked to many factors inside and outside the workplace. It can be a safety and health hazard for the fatigued person and a safety hazard for those who work around them. Fatigue is often caused by several interrelated factors which can be cumulative or build up over time to become hazardous. It is not just about lack of sleep, eating properly, working extended hours/shift work, or doing physically challenging work. We will explore all the factors that result in worker fatigue, and how employers and workers can manage it.