<p>Stress concentrations at sharp tunnel corners can amplify localized stresses, promoting crack initiation, progressive damage, and premature instability of the surrounding rock mass. Despite its engineering significance, the influence of corner geometry on the behaviour of footing–tunnel systems has received limited attention. This study investigates the effect of corner rounding on rectangular tunnels in rock masses of varying strengths subjected to footing-induced loading. Finite element analyses were performed to evaluate the influence of corner radius ratio (<i>r/B</i>), cover depth (<i>C/H</i>), and rock mass strength on load–settlement behaviour, ultimate bearing capacity, and failure mechanisms. The results demonstrate that corner rounding effectively reduces stress concentration and promotes a more uniform stress redistribution around the tunnel. At a shallow cover depth (<i>C/H</i> = 1), increasing <i>r/B</i> from 0 to 0.25 improves the ultimate bearing capacity by up to 18.4% and 9.3% in low and medium-strength rock masses, respectively, while the improvement is less significant in high-strength rock&#xa0;masses,&#xa0;owing to their greater inherent resistance to stress concentration at sharp corners. The beneficial influence of corner rounding decreases with increasing cover depth (<i>C/H</i> = 2–4), where overburden stresses become the dominant controlling factor. Failure analyses reveal a transition from highly localized, corner-dominated shear zones in sharp-edged tunnels to smoother and more continuous failure surfaces in rounded geometries. Among the investigated configurations, a corner radius ratio of <i>r/B</i> = 0.25 provided the most favourable footing response under shallow cover conditions. The findings highlight the importance of tunnel corner geometry in improving the stability and load-carrying performance of foundation systems constructed above rectangular rock openings.</p>