Traumatic abdominal wall hernias remain relatively rare entities despite the increased incidence of blunt trauma. Mechanisms reported in the literature include a combination of a sudden increase in intra-abdominal pressure and powerful shear forces applied to the abdominal wall. These hernias are noteworthy in that they may be associated with significant intra-abdominal injuries. We describe a novel form of traumatic hernia with a unique mechanism. A blunt force leads to the fracture of a rib and penetration of the abdominal wall by the jagged costal remnant, creating a hernia defect. This autopenetrating hernia is presented in the context of a classification scheme for traumatic abdominal wall hernias.