A stress fracture represents the inability of the skeleton to withstand repetitive bouts of mechanical loading, which results in structural fatigue and resultant signs and symptoms of localized pain and tenderness. To prevent stress fractures, an appreciation of their risk factors is required. These are typically grouped into extrinsic and intrinsic risk factors. Extrinsic risk factors for stress fractures are those in the environment or external to the individual, including the type of activity and factors involving training, equipment, and the environment. Intrinsic risk factors for stress fractures refer to characteristics within the individual, including skeletal, muscle, joint, and biomechanical factors, as well as physical fitness and gender. This article discusses these extrinsic and intrinsic risk factors, as well as the pathophysiology and epidemiology of stress fractures.