The ROK has experienced unprecedented rapid urbanization since the Korean War. Cities have been critical engines for economic development as hubs of innovation and efficiency. However, they have also faced diverse urban challenges during the process of swift urbanization. Thus, the urbanization process needs to be assessed through the lens of sustainability, based on an integrated approach that evaluates the performance of the ROK and provides implications for developing countries. Against this backdrop, this chapter aims to assess the urban sustainability of the ROK using the framework of the SDGs; it focuses on Goal 11 from 1980 to 2015, drawing lessons for the ROK to move forward. The results from the analysis demonstrate that the ROK has been making a steady improvement in urban sustainability over time. However, the analysis of each indicator reveals significant variability in progress, showing unevenness in the level of progress across different areas. In addition, the analysis shows that pursuing one target could conflict with the implementation of another target, calling for careful attention to comprehensive and integrated policymaking based on collaboration across sectors.