The experience of fatigue is common to all human beings, since fatigue is a naturally occurring state of being. In occupational settings, fatigue can pose a threat to people, equipment, the environment, and corporate reputations. Although significant progress has been made in terms of understanding the causes of, and solutions for, worker fatigue, a great deal of complexity remains. This complexity is partly related to the fact that individuals are different in many ways (e.g., in terms of their genetically determined sleep need) and because of the general biological, psychological, and social components of personal fatigue. This chapter focuses on key fatigue-related principles, terminology, example frameworks, and key issues now and in the foreseeable future. The challenges for industry relate to both opportunities and potential threats, such as automation, fatigue-monitoring technologies, staffing levels, cultural differences within the workforce, and the remote locations of many operations. With evidence-based program development and evaluation, enhanced fatigue management can deliver improvements in safety, compliance, operational flexibility, worker satisfaction, and other relevant metrics. The lustre of diamonds is invigorated by the interposition of darker bodies; the lights of a picture are created by the shades. The highest pleasure which nature has indulged to sensitive perception is that of rest after fatigue.-Samuel Johnson (1825, p. 319) T he human experience of fatigue is as old as humanity itself, since fatigue is a naturally occurring state of being. Since the 19th century, the concept of worker fatigue in occupational settings has been researched and documented. Initial comprehensive accounts, most with a focus on physical aspects, have been clearly summarized (see 573947R EVXXX10.