<p>The growing demand for sustainable materials in the pavement industry has spurred research into bio-based and waste-derived modifiers to improve asphalt performance and promote sustainable waste management. Among these, lignin, a naturally occurring biopolymer, has garnered significant attention for its potential to enhance asphalt binders and mixtures. This study investigates the innovative use of Olive Pomace Lignin (OPL), a bio-polymer extracted from raw olive pomace waste, as a sustainable additive in asphalt binders and mixtures. The OPL was incorporated into asphalt cement (60/70 grade) at dosages ranging from 4 to 14%, and comprehensive experimental evaluations were conducted to assess its mechanical and rheological impacts. The results reveal that OPL significantly enhances binder stiffness, thermal stability, and resistance to deformation, with a 29% increase in Marshall stability and a softening point improvement to 57&#xa0;°C at the optimal dosage of 10%. Modified binders demonstrated superior rutting resistance while maintaining workability. Mixtures incorporating OPL exhibited enhanced load-bearing capacity and deformation resistance, achieving a balance of stiffness and flexibility at the 10% dosage. However, higher concentrations (&gt; 10%) resulted in diminished ductility and increased phase separation, underscoring the importance of dosage optimization. The practical significance of these findings is further reinforced by an economic impact analysis, which highlights a Benefit–Cost Ratio (BCR) of 0.20 at the optimal 10% OPL dosage, alongside 18% cost savings compared to polymer-based modifiers. The environmental benefits include minimized CO₂ emissions due to processing temperatures consistent with unmodified asphalt binder. This study shows that OPL is a high-performance, cost-effective, and sustainable asphalt binder modifier, paving the way for agricultural byproducts in infrastructure development.</p>