Elevated levels of naturally occurring radionuclides (²³⁸U, ²²⁶Ra, ²³²Th, and ⁴⁰K) present significant global environmental and public health challenges due to their increasing radio-ecotoxicological effects. Numerous localized studies have examined natural radioactivity within the Bengal Basin (BB), but comprehensive regional-scale assessments remain limited. This review synthesizes thirty years of research to provide a thorough understanding of radionuclide contamination levels, environmental dynamics, and the associated ecological and human health risks within the BB. Radiation exposure levels from key environmental components, such as soil, water, sediment, and biota, are evaluated and compared with international standards, revealing that the southeastern and central parts of the basin frequently exhibit activity concentrations at or above global averages. The review further highlights the ecotoxicological implications of radionuclide accumulation in food chains and aquatic and terrestrial ecosystems, underscoring potential dose-related health effects. Four principal remediation and management strategies—source identification, environmental surveillance, dose evaluation, mitigation, and policy implementation—are discussed in the context of sustainable environmental governance. Finally, the study establishes explicit links between natural radioactivity management and the United Nations Sustainable Development Goals, particularly SDG 12.4 on responsible chemical and waste management. Overall, these findings point to the urgent need for coordinated monitoring, mitigation, and policy integration to ensure radiological safety and long-term environmental sustainability in the BB and comparable deltaic regions worldwide.