This chapter describes what is currently known about fatigue after stroke. It develops a working definition and discusses some theories and identifies some potential mechanisms that may account for poststroke fatigue. The chapter characterizes physiologic and biochemical dimensions, work performance and behavioral components, and symptom-sensory elements. It identifies predisposing factors and outlines the assessment of fatigue in individuals with stroke, along with proposed management strategies to reduce symptom distress and promote function and well-being. The chapter suggests research directions to further develop knowledge about the mechanisms and features of poststroke fatigue that may lead to effective rehabilitation interventions to reduce its impact. Combined with the motor deficits, cardiovascular and metabolic deconditioning, sleep disorders, and social isolation that often accompany neurological impairment, poststroke fatigue is associated with disruptions in physical, occupational, and social functions.