Background: The Judet-Letournel classification has been widely used to diagnose acetabular fractures since it was proposed. However, there has been growing evidence of incompleteness and comprehension difficulty in this classification, which may adversely affect its clinical use. The purposes of this study were to introduce a novel 3-column classification system for acetabular fractures and to evaluate its reliability and reproducibility. Methods: A total of 1,028 patients with acetabular fractures, who had undergone surgical treatment from June 2011 to January 2017 in 7 level-I trauma centers, were recruited into this study. Preoperative radiographs and computed tomographic (CT) scans were conducted for each patient. To evaluate the reproducibility of the 3-column classification system for acetabular fractures, the interobserver and intraobserver reliability (kappa coefficient, kappa) of this classification system compared with those of the Judet-Letournel classification system was investigated by 4 observers. Results: A total of 209 patients (20.33%) could not be classified by the Judet-Letournel classification, and 3 cases (0.29%) could not be classified by the novel 3-column classification. The mean kappa value of the interobserver reliability for the Judet-Letournel classification was 0.591 (range, 0.508 to 0.681), indicating moderate agreement, whereas the mean kappa value was 0.735 (range, 0.594 to 0.930), indicating substantial agreement, when using the 3-column classification. The mean kappa value for the intraobserver reliability was 0.751 (range, 0.708 to 0.793) for the Judet-Letournel classification and 0.909 (range, 0.792 to 0.957) for the 3-column classification. Conclusions: The 3-column classification, based on the anatomic character of the acetabulum, showed higher interobserver and intraobserver reliability than the Judet-Letournel classification. Additionally, certain fracture patterns in the 3-column classification scheme generally correlated with surgical approaches. This novel classification system may be used as a supplement to the traditional Judet-Letournel classification system.