Pain is a complex physiological and emotional experience that serves as a vital protective mechanism, but when unmanaged, it becomes a significant source of distress and suffering. In nonhuman primates, whose physiological and behavioural responses closely resemble those of humans, the recognition and alleviation of pain require both sound scientific understanding and ethical sensitivity. This chapter examines the physiology of pain and the fundamental principles of analgesia in nonhuman primates. It describes how pain arises and can be modulated through various classes of analgesics, including opioids, local anaesthetics, NMDA receptor antagonists, α₂-adrenoreceptor agonists and anticonvulsant agents. The key aspects of pain management, prevention, assessment and treatment are outlined, with emphasis on accurate recognition and humane intervention. Finally, the chapter considers situations where pain can no longer be controlled, highlighting the importance of setting humane endpoints and providing appropriate euthanasia. The prevention and alleviation of pain are essential to ensuring responsible and humane practices in nonhuman primate research.