Abstract: This study examined the effect of agile project management practices on the successful implementation of the Gigawatt Solar Power Project in Rwamagana District, Rwanda. Specifically, the study examined the effect of agile planning, assessed the influence of stakeholder collaboration, and evaluated the effect of iterative methods on successful project implementation. The study was guided by Agile Project Management Theory, Stakeholder Theory, and Dynamic Capabilities Theory. A descriptive and correlational research design using quantitative and qualitative approaches was adopted. The study targeted 230 respondents. Quantitative data were analyzed using SPSS version 25 through descriptive statistics, Pearson correlation, and multiple regression analysis, while qualitative data were analyzed thematically. The findings revealed that agile planning, stakeholder collaboration, and iterative methods had positive and statistically significant effects on successful project implementation. The three agile project management practices jointly explained 68.9% of the variation in successful project implementation (R² = 0.689). Stakeholder collaboration was the strongest predictor (β = 0.408, p < 0.001), followed by agile planning (β = 0.380, p < 0.001) and iterative methods (β = 0.219, p < 0.001). The study concluded that strengthening agile planning, stakeholder collaboration, and iterative methods improves timely completion, budget compliance, and quality achievement. The study recommends strengthening stakeholder engagement mechanisms, institutionalizing agile planning practices, and promoting continuous review and improvement throughout the project lifecycle.