© 2015 by Human Factors and Ergonomics Society 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.