This chapter presents a narrative review of urban water management and sustainability in Freetown, Sierra Leone, focusing on challenges, opportunities, and innovations in rainwater harvesting (RWH) and water reuse. It contextualizes Freetown’s water crisis within broader global trends, rapid unplanned urbanization, and climate-induced water scarcity, while grounding analysis in local realities: 1.1 million residents rely on the aging and overburdened Guma Reservoir, yet only 1–57% of the population has reliable access to safe drinking water. Freetown’s tropical climate, pronounced seasonal rainfall variability, and inadequate regulations in rapid urban expansion further exacerbate strains on outdated water infrastructure. The review identifies key technical and governance barriers to sustainable water management, including significant pipeline transmission losses, Guma Reservoir sedimentation, pervasive water contamination risks, fragmented institutional governance, and chronic funding constraints. It subsequently highlights opportunities through integrated frameworks such as Water Sensitive Cities (WSC) and Sustainable Urban Water Management (SUWM), approaches that prioritize ecosystem protection, multi-stakeholder collaboration, and decentralized water systems. Finally, the chapter evaluates two contextually tailored innovations: (1) RWH, which can reduce potable water demand by 30–92% when designed to accommodate Freetown’s dense informal settlements; and (2) advanced water reuse technologies (e.g., IFAS–MBR systems), which produce high-quality treated effluent with lower carbon emissions but face persistent challenges related to phosphorus removal and compliance with updated water treatment directives. Collectively, these insights establish a foundation for developing targeted, sustainable water solutions aligned with Freetown’s rapidly evolving urban landscape.