Bone stress injuries occur when forces applied to a bone for an extended period exceed the ability of the bone to adequately remodel. These injuries, which range from stress reactions to nondisplaced and even displaced fractures, most often affect people who experience high levels of repetitive stress and loading in the lower extremity or changes in physical activity level. For example, stress fractures are common in endurance athletes, in athletes engaged in preseason and early-season conditioning, and in military recruits. In the military, these injuries are most often encountered during basic training, when new recruits undergo the rigors of intense physical activity to which they may not be accustomed. Female athletes and athletes with poor nutritional status are at elevated risk for injury. Bone stress injuries are difficult to diagnose with radiographs alone. Making the correct diagnosis may require a combination of physical examination, advanced imaging, and an index of suspicion. Differences in injury location account for variations in risk for nonunion, displacement, and other complications. For low-risk injuries, treatment typically consists of reduced weight-bearing for several weeks with gradual return to activity. Higher-risk injuries need to be closely monitored for progression and may require operative intervention. Even after surgery, some types of stress fractures may take several months to achieve radiographic union. In addition, underlying nutritional or metabolic deficiencies may need to be treated to prevent future injuries. In this article, we review the diagnosis, management, and prevention of bone stress injuries with a focus on more serious manifestations, such as stress fracture.