Macroalgae, or seaweeds, are increasingly recognized as valuable resources in the field of environmental remediation due to their high productivity, adaptability, and rich biochemical composition. Native macroalgae play a direct role in remediating aquatic ecosystems through mechanisms such as biosorption, bioaccumulation, and nutrient uptake. Additionally, processed macroalgal products such as alginates, carrageenans, biochar, and polysaccharide-based materials exhibit enhanced capabilities for removing heavy metals, dyes, pharmaceuticals, and excess nutrients from contaminated water and soils. This chapter reviews recent advances in practical applications and the dual potential of macroalgae and their derived products in wastewater treatment, soil remediation, and integrated bioremediation systems to remove pollutants. Environmental benefits, scalability, economic feasibility, and sustainability aspects will also be discussed, positioning macroalgae as promising agents and material sources for next-generation green remediation technologies.