This chapter explores the hydrology of the Ogooué (Gabon) and Sanaga (Cameroon) river basins—two critical but understudied watersheds within the broader Central African hydro-ecological system. While both rivers discharge independently into the Atlantic Ocean, they are closely tied to the Congo Basin Forest through shared climatic drivers, ecological continuity, and significant contributions to regional water cycles and biodiversity. The chapter provides an in-depth analysis of their geomorphology, hydrological regimes, and socioeconomic importance, highlighting the Ogooué’s largely pristine, forest-dominated catchment and the Sanaga’s heavily regulated hydrosystem dominated by hydropower infrastructure. Long-term observational and satellite data reveal trends of declining rainfall and altered discharge regimes in both basins since the 1970s, driven by climate change and land use transitions. Advanced hydrological modeling—using satellite altimetry, GRACE, and distributed models like SWAT and MGB—demonstrates spatial variability in hydro-climatic responses and emphasizes the need for integrated, context-specific water resource management strategies. The chapter also stresses the ecological significance of these rivers, which host diverse fauna and flora, and underscores the role of traditional ecological knowledge in managing dynamic wetland systems. A call is made for increased scientific investment in Central Africa, where hydrological data scarcity and low international funding hinder evidence-based conservation and development planning. Recognizing the Ogooué and Sanaga as vital components of the Central African hydrological mosaic is key to enhancing resilience and sustainability in the face of rapid environmental change.