Despite adequate control of disease activity with standard medical therapies, there remains an ongoing need for complementary and interventional approaches for the management of persistent back pain in patients with ankylosing spondylitis. Although the erector spinae plane block has been described in the literature as a safe and effective analgesic intervention for chronic back pain in various patient populations, to the best of our knowledge, no clinical study has specifically evaluated its use for persistent back pain in patients with ankylosing spondylitis receiving medical treatment. Therefore, the present study aims to evaluate the effects of erector spinae plane block on pain severity and clinical outcomes in patients with ankylosing spondylitis whose disease activity is controlled under treatment but who continue to experience persistent back pain.