<p>This study’s objective is to investigate how nano titanium dioxide at various dosages affects the shear strength, cohesion, and angle of internal friction of natural sandy soils with varying gypsum amounts from three different locations, S1, S2, and S3, in Tikrit, Iraq. Consolidated undrained triaxial shear strength tests are conducted to investigate the shear resistance of the tested gypseous soils stabilized with NTD and compared with untreated soil samples in both saturated and unsaturated states. The results of the consolidated undrained triaxial shear strength tests conducted on the treated soils with NTD as an additive at different percentages, 0.1%, 0.3%, and 0.5%, illustrate that the shear strength value increased as the NTD percentage increased. Significant increases in overall shear strength, specifically for S1, are consistently demonstrated by 0.5% of NTD. According to test results under saturated conditions, cohesiveness increased significantly as NTD increased, particularly at 0.5% NTD, for S1, S2, and S3. Simultaneously, when the percentages of NTD increased, the angle of internal friction climbed slightly at varying rates. According to these results, only small traces of NTD may be an advantageous agent for stabilizing collapsible gypseous soils in civil engineering projects and providing more dependable ground support in regions with similar types of soil. Advances in applying NTD are thus opening new avenues for enhancing soil stabilization techniques and ensuring the longevity of engineering structures.</p>