Background: Spinal anesthesia is widely used for infraumbilical and lower limb surgeries due to its cost-effectiveness, simplicity, and ability to provide profound analgesia with minimal metabolic alterations. Bupivacaine, though effective, has been associated with prolonged motor block and cardiovascular effects. Ropivacaine, a newer alternative, provides a differential block with minimal motor blockade, potentially allowing early ambulation. The addition of fentanyl enhances the anesthetic effect while reducing the required local anesthetic dose. This study aims to compare the efficacy and safety of hyperbaric 0.5% bupivacaine with fentanyl and isobaric 0.75% ropivacaine with fentanyl in spinal anesthesia. Methods: A prospective, randomized, double-blind study was conducted on 66 ASA I-II patients aged 20–60 years undergoing infraumbilical and lower limb surgeries. Patients were allocated into two groups: Group A received intrathecal hyperbaric 0.5% bupivacaine (3 ml) with fentanyl (25 mcg), and Group B received intrathecal isobaric 0.75% ropivacaine (3 ml) with fentanyl (25 mcg). Sensory and motor block onset, duration, hemodynamic stability, and perioperative complications were assessed. Results: Both groups achieved adequate sensory blockade for surgery. Group A (bupivacaine) had a faster onset of sensory and motor blockade but also a longer duration of motor block. Group B (ropivacaine) exhibited a shorter motor block duration, allowing for earlier ambulation while maintaining effective analgesia. Hemodynamic parameters remained stable in both groups, with a lower incidence of hypotension in the ropivacaine group. Conclusion: Isobaric 0.75% ropivacaine with fentanyl provides comparable surgical anesthesia to hyperbaric 0.5% bupivacaine with fentanyl but offers a shorter motor block duration, making it a preferable option for procedures requiring early ambulation. The study supports the use of ropivacaine as a safer alternative with minimal hemodynamic alterations.