Latin American public transport (PT) systems are the backbone of urban transport with high ridership levels but at the same time, they face substantial deficits in terms of their sustainability. No comprehensive framework for PT sustainability assessment exists so far that is tailored to the specific local situation in this region. Therefore, this study develops for the first time a theoretically sound and feasible index for assessing the sustainability of PT systems in Latin America, the Sustainable Public Transport Index for Latin America (SPTI-LATAM). The index is based on an Assessment Indicator Model (AIM) with overall 49 indicators in the five dimensions system effectiveness, social, environmental, economic, governance and integrated transport planning. The SPTI-LATAM is designed with three levels: 1) the basic index (BSPTI) containing 32 indicators; 2) the extended index (ESPTI) including 11 additional indicators; and 3) the global index (GSPTI) with 6 additional indicators. The BSPTI is computed for eleven case study cities to demonstrate its feasibility and to analyze the sustainability of PT systems in the region. The framework uses the Equal Weighting Aggregation (EWA) method for assigning weights to each indicator, the Weighted Sum Model (WSM) for aggregating the indicators to the overall index and international standards and benchmarks for normalization. The final scores of the BSPTI show that the case study cities have still challenges to reach sustainability since only two cities had scores slightly higher than the half of achievable points (55 and 51), while eight cities had scores between 40 and 50 points, and one city achieved 39 points. Deficits are identified mainly for PT service quality, for the environmental performance, for the governance dimension and less for PT system coverage. Overall, the analysis of the BSPTI-LATAM for the 11 case study cities shows that the index is suitable for benchmarking sustainability of local PT systems and ready to be used in research and practice.