The Soledade – Ió Grande 1 Hydroelectric Project is the anchor investment in São Tomé and Príncipe's energy transition, designed to structurally transform the energy landscape in the south of the island. Located in the village of Soledade, in the district of Caué, the project takes advantage of the high water potential of the Ió Grande River – a 73.8 km² basin with an estimated installed capacity of 6.9 MW and an average annual production of 26.5 GWh, already validated by the 2021 technical and environmental study. With a 43-metre dam and reliable, predictable energy, the plant will replace around 30% of national diesel consumption, reducing ~17,000 tCO₂/year, substantially lowering public spending on fossil fuels and strengthening the security and stability of the electricity grid. This infrastructure simultaneously guarantees clean and affordable energy for communities and the productive sector, while strengthening the country's climate resilience. Structured as a BOT (Build–Operate–Transfer) PPP, with a 25–30-year concession, the project presents a solid framework of attractiveness for investors: CAPEX of €51.5 million, IRR up to 8.78%, ROI of 12% and payback of 7 years, supported by a PPA contract in euros secured by EMAE. Promoted by DGRNE and operated by EMAE, Ió Grande 1 benefits from the involvement of strategic partners such as the AfDB, the European Union, the UNDP and the Green Climate Fund, ensuring alignment with international standards and robust mitigation of environmental and social risks. This is a unique green investment opportunity in a country that is taking the decisive leap towards a clean, resilient and competitive energy matrix.