Abstarct: The objective of this research is to evaluate the effects of three types of natural biopolymers—Chitosan, Guar Gum, and Sodium Alginate—on improving the geotechnical properties of collapsible soil in Golestan Province. Due to their unstable structure, collapsible soils undergo sudden settlement and loss of strength when exposed to moisture and loading; therefore, the use of natural and sustainable materials can serve as an effective solution and a suitable alternative to chemical stabilizers. In this study, the Unconfined Compressive Strength (UCS) test was conducted as the primary experiment, utilizing three concentrations (0.5%, 1%, and 1.5%) for each biopolymer across three curing periods (1, 7, and 28 days). These tests were performed under various thermal conditions, including ambient temperature (25-30°C), high temperature (60°C), and confined environments (5°C and 25-30°C).The results indicated that the addition of biopolymers generally increases the compressive strength and cohesion of the soil. In the short term (7 days), specimens containing Guar Gum cured at 60°C exhibited the highest strength, showing an increase of over 115% compared to the control sample. In the long term, specimens cured at ambient temperature (25-30°C) demonstrated more stable performance and greater durability. Double consolidation tests, performed with a 1.5% concentration of Guar Gum and Chitosan after a 7-day curing period at ambient temperature, showed a reduction of more than 70% in collapse potential. Furthermore, Atterberg limits results revealed that the addition of Sodium Alginate and Chitosan increases the plastic limits of the collapsible soil, whereas the addition of Guar Gum led to a loss of plasticity and the elimination of Atterberg limits using the Casagrande method. Standard compaction test results also showed that as biopolymer content increases, the optimum moisture content increases while the maximum dry unit weight decreases relative to the pure soil. Overall, the findings suggest that natural biopolymers—particularly Guar Gum—can serve as efficient, economical, and sustainable alternatives to traditional stabilizers for the improvement of collapsible soils by enhancing strength and stability while reducing collapse potential.