Alginate has gained extensive attention due to its versatile properties and numerous applications in different fields. Due to the abundant availability of raw alginate in nature and its advantage of being easily recycled, alginate-based materials are conducive to advancing the shift away from an economy dependent on fossil fuels to a more environmentally friendly and sustainable one. In addition, its inherent biocompatibility makes alginate a fascinating biomedical material. This comprehensive review presents a detailed analysis of alginate, focusing on its structural characteristics, physicochemical and biological properties, current processing technologies, and modification strategies. This review explores the diverse applications of alginate-based materials in biomedicine and healthcare, considering drug delivery systems, tissue engineering, and wound dressings. Additionally, this review looks into the environmental applications of alginate in biosensors and waste-water treatment. The challenges associated with alginate utilization and future perspectives for research and development are also presented. This review provides a comprehensive overview of alginate, offering valuable insights into its properties, applications, and potential for future applications across various industries.