The interscalene block is a widely used regional anaesthesia technique for shoulder and upper limb surgeries, providing adequate analgesia and reducing opioid requirements. This technique targets the brachial plexus at the level of the C5–C7 roots, situated within the interscalene groove between the anterior and middle scalene muscles. The block can be performed using landmark, nerve stimulation, or ultrasound-guided techniques, with ultrasound improving precision and safety. Key complications include phrenic nerve palsy, Horner’s syndrome, vertebral artery puncture, and pneumothorax. Modifications such as lower local anaesthetic volumes, extrafascial injections, or alternative nerve blocks (e.g., suprascapular and axillary blocks) can reduce risks. Continuous catheter techniques provide prolonged postoperative analgesia in major surgeries like shoulder arthroplasty.