Good sleep and adequate physical activity are essential to health. Yet, large numbers of people are chronically deficient in sleep and physical activity. About 1 in 3 Americans get less than 7 h of sleep per night and only 1 of 4 adults regularly complete weekly physical activity in amounts recommended for good health. This chapter reviews research that has examined relationships between regular physical activity and sleep. The overall weight of evidence supports that regular physical activity is associated with better sleep quality among healthy adults, with epidemiological studies showing moderate-sized effects and more well-controlled randomized controlled trial experiments often showing larger effects. Large epidemiology studies suggest that the relationship between regular physical activity and better sleep quality may partially mediate the well-established associations between physical activity and reduced risk of mortality, cardiovascular diseases, and dementia. There is evidence that the completion of regular physical activity also is associated with better sleep quality among those with certain sleep disorders (i.e., insomnia, obstructive sleep apnea, and restless legs syndrome), mental health disorders (i.e., depression and posttraumatic stress disorder), and medical illnesses (i.e., breast cancer survivors). The evidence is inadequate to support that regular physical activity substantially improves sleep quality either (i) in children, adolescents, and older adults, (ii) in those with cancers except for breast cancer, (iii) in those with fibromyalgia, or (iv) among those with chronic kidney disease. Also, there is inadequate evidence to conclude that sleep quality is disrupted during weeks when competitive athletes engage in periods of overtraining.