A countrywide benchmarking of ultimate recovery factor (URF) for oil reservoirs in Kuwait is presented in this study. The results of this study have been useful to support identification of long-term opportunities and have influenced the creation of conceptual development plans for some of the newly discovered prospects of the company. The Kuwait Oil Company (KOC) has a diverse inventory of petroleum reservoirs having a wide range of geologic age, depth, reservoir complexity, and development maturity. This study focused on the reservoir complexity index (RCI) method and global analogs to identify development opportunities and improvements to the URF in the brown and green fields of Kuwait. A customized benchmarking workflow was developed to assess the URF of approximately 100 conventional oil reservoirs. First, a detailed 17-parameter RCI factor and a simplified 7-parameter RCI factor were developed. These two RCI methods were then validated against simulation-estimated URF from waterflood development for the study reservoirs. Next, the two RCI factors were used to benchmark URF for study reservoirs against the company's peers and against global analogs having best practices in operations. Finally, a set of benchmarking dashboards were refined to identify reservoir-complexity concerns, comparisons of company and global peers, and identification of potential upsides or risks in URF. Comparison of higher performing global analogs to the company's reservoirs with similar RCI resulted in identification of additional development opportunities and upsides in URF.