Abstract: This study explores the impact of capital structure on enterprise market value, specifically examining the influence of the debt ratio on the market valuation of S&P 500 companies. Capital structure decisions are crucial for corporate managers and investors, as they significantly affect firm performance, risk, and market perception. The research is motivated by the need to understand how financial leverage influences market valuation, particularly in large, publicly traded companies. Utilizing two-way fixed effect panel data models spanning from 2020 to 2023, we find significant evidence that higher leverage is associated with an increase in market valuation, offering a comprehensive view of the factors that influence corporate market values. Additionally, the study reveals that the impact of leverage varies across company sizes and examines sector-specific effects and the role of long-term debt. The findings provide key insights for investors and corporate managers regarding the impact of financial structure on company valuation, emphasizing the importance of optimizing capital structure to enhance firm value and strategic decision-making.