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The escalating impacts of climate change pose a significant risk to South Africa’s water resources and infrastructure, particularly as a result of increased frequency and intensity of extreme rainfall. This study presents extreme rainfall projections for the country by analysing Phase 6 of the Coupled Model Intercomparison Project (CMIP6) Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) global climate models (GCMs) from 2020 to 2100, under SSP1-2.6 and SSP5-8.5 scenarios. Five models and their ensembles were evaluated against ECMWF ERA5-Land and station data using Taylor diagrams, NSE, RMSE, PBIAS, and R². The ensemble outperformed individual models, which showed a similar spatial bias, underestimating rainfall over the escarpment while overestimating it in the lowlands. Rainfall changes were analysed for the near- (2020–2055) and far-future (2065–2100), focusing on the 5th, 50th, and 95th percentiles. Future midlatitude and subtropical circulation changes were projected to intensify the west-east rainfall gradient, leading to a drier west and a wetter east. This trend drives an overall increase in extreme rainfall events across South Africa. Annually, this is reflected in drier conditions projected along the coast and northeast in the far-future (5th and 50th percentiles), while the eastern half will likely experience increased extreme wet conditions (95th percentile). January projects rainfall increases in the eastern interior, with extreme wet conditions increasing by 35–45 mm across scenarios. Conversely, October may experience increased extreme dry conditions (5th percentile), with more than 48 mm decrease in the far-future under SSP5-8.5. During austral summer (DJF), pronounced wet and dry extremes are projected over eastern South Africa. Austral winter (JJA) will likely experience persistent and intensifying dry and wet extremes along the coast, with the southwest Cape particularly vulnerable to severe dry conditions. Heavy rainfall days are projected to increase in eastern South Africa, exceeding 10 days in the eastern interior. This study is crucial for understanding rainfall extremes under a changing atmospheric circulation and unpins more effective climate change adaptation strategies in South Africa.