Sustainable soil stabilization is causing increased interest in geotechnical engineering as a method to improve the properties of soil while reducing the impact on the environment. This study investigates two promising methodologies: biopolymer-based stabilization and geopolymer-based stabilization. Biopolymers, like xanthan gum and guar gum, enhance soil strength by hydrogen bonding and particle encapsulation, providing advantages such as renewability, little carbon impact, and ease of application. However, issues like as water sensitivity and biodegradation limit their long-term effectiveness in the field. Geopolymers, made from industrial wastes such as fly ash and ground granulated blast furnace slag (GGBFS), establish rigid aluminosilicate networks by alkaline activation, greatly enhancing soil strength, durability, and environmental sustainability. Despite these advantages, geopolymers require careful control of activator concentration and curing conditions, and concerns persist over activator management and variability at field scale. Hybrid biopolymer–geopolymer stabilization is offered as an innovative approach that integrates the mechanical performance, durability, and environmental sustainability by recognizing the mutually beneficial strengths and limitations of both technologies. Identified research gaps include the need for extended field studies, improved mix design methodologies, and thorough environmental effect evaluations. This analysis emphasizes the potential of hybrid systems for improving sustainable soil stabilizing methods and provides future research possibilities for developing these technologies in road subgrade and infrastructure applications.