Illegal sand mining has become a serious environmental and developmental issue across many of India’s riverine regions, especially in ecologically sensitive floodplain districts like Murshidabad in West Bengal. The district’s economy, settlement patterns, and ecological stability depend closely on the Bhagirathi and other rivers, which sustain agriculture, fisheries, groundwater recharge, and transport. Unregulated extraction, however, has upset sediment balance, hastened bank erosion, changed channel morphology, reduced the quality of aquatic habitats, and deepened livelihood insecurity for rural households. This paper investigates the effects of illegal sand mining on river ecology and local livelihoods in Murshidabad through a qualitative, desk-based analysis. It draws on scholarly literature, policy documents, and institutional reports to show how sand mining produces both ecological damage and socio-economic vulnerability. The findings suggest that illegal mining can offer short-term income and employment, but over time it contributes to farmland loss, declining fishery resources, groundwater stress, and weaker community resilience. In Murshidabad, the paper argues, sustainable development will require stronger environmental governance, community participation in monitoring, ecological restoration, and more varied livelihood options. River protection, the article concludes, is inseparable from rural development. This study explores how illegal mining impacts riverine ecosystems, local livelihoods, and the broader quest for sustainable rural development.