The olive oil supply chain generates a substantial number of by-products, presenting significant environmental, economic, and social challenges. However, these by-products, such as pomace, wastewater, and biomass, also offer valuable opportunities for implementing a circular economy (CE) model that enhances sustainability. Despite increasing attention to the valorization of these by-products, understanding of the indicators used to measure circularity in this context remains limited. This systematic review examined the existing literature on circular economy indicators employed to assess the use of by-products in the olive oil supply chain. The aim was to provide a comprehensive overview of the most suitable indicators in this sector, while identifying best practices for quantifying and monitoring progress towards a more circular system. The review followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, and bibliometric analysis was conducted using CiteSpace 6.4 R1 software. The results highlighted a key indicator, the Material Circularity Indicator (MCI). Additionally, methodologies such as Life Cycle Assessment (LCA) and water footprint (WF) were evaluated, while challenges were identified, including the need for standardized metrics and improved data collection across the supply chain. This review provides valuable insights for both future research and policy decisions aimed at promoting sustainability and circularity in the olive oil industry.