This chapter provides a broad overview of the biomechanics of the human thorax with a focus on impact loading. The introduction to the thoracic anatomy emphasizes its skeletal structures, organs and soft tissues, and this is followed by a brief description of injury quantification using the Abbreviated Injury Score and Injury Severity Score. Injury mechanisms are reviewed from a historical perspective. They include rib fractures and flail chest, lung contusions, hemo- and pneumo-thoraces, and heart and aorta injuries. The next two sections are focused on frontal and side impact injury aspects. In the frontal impact, different methods used in loading are described, including blunt, belt and airbag loading, along with biomechanical response data and injury mechanisms. Various candidates for injury criteria are also described. Pure lateral and oblique side impacts are then described using a similar method, albeit separately. The oblique loading modality discovered in modern vehicular environments is relatively new. Oblique impacts are shown to be more injurious than pure lateral impacts. Injury criteria associated with this vector needs further research as studies are beginning to appear in published literature. The reader is then exposed to a brief assessment and development of dummy thorax although dummy-related topic is covered elsewhere in the book.